Tax documents

1095-A vs. 1095-B vs. 1095-C: the one you need, decoded

Three forms document your health coverage under the ACA, and the letter decides everything: the 1095-A comes from a Marketplace and your return may be rejected without its numbers, while the 1095-B and 1095-C are records you keep and never file. Granite's schema library tracks 19 fields across the three variants, and only three of them, the annual premium, SLCSP (second-lowest-cost Silver plan), and advance premium tax credit (APTC) totals in Part III of a 1095-A, ever land on a tax return. This guide is the sorting test and the box-by-box read of the A, with a worked Form 8962 example. It also covers the two recent rule changes: furnish-on-request and the returning 400% cliff.

21 min read · Updated 2026-08-24

The header test: which 1095 are you holding?

Read the title printed at the top of the form. It says one of three things, and that line decides what the document is and what you have to do with it.

  • “Health Insurance Marketplace Statement” means this is a 1095-A. It came from healthcare.gov or your state exchange, and if advance premium tax credit was paid on your policy, your tax return needs its numbers.
  • “Health Coverage” means this is a 1095-B. It came from an insurance company, a government program like Medicare, Medicaid, CHIP, TRICARE, or VA care, or a small self-insured employer. It proves you had coverage. You keep it. That’s the whole job.
  • “Employer-Provided Health Insurance Offer and Coverage” means this is a 1095-C. It came from an employer with 50 or more full-time employees and documents what coverage they offered you. Also keep-only.

We can vouch for the header test because it’s the same test our software runs. Granite’s document schema library models all three 1095s as one document type with a variant, precisely because the family confuses people (and, for what it’s worth, machine classifiers) so reliably, and the variant is derived from a single line: the header text. If you learn nothing else from this page, learn the three headers. The deeper tells all agree with them: a monthly grid of dollar figures in Part III means A, a one-letter origin-of-coverage code on line 8 means B, and a grid of codes like 1E and 2C on lines 14 through 16 means C.

The 1095 family is the health-insurance wing of the same January paperwork wave that brings your W-2 and 1099s. The difference is that those forms report income, while a 1095 reports coverage, and only one member of the family carries numbers your return depends on.

The three forms, side by side

The whole comparison reduces to one row of the table below: only the 1095-A is ever needed to file, and none of the three is attached to your return. Everything else, who sends it, when, what’s on it, follows from the sender.

Forms 1095-A, 1095-B, and 1095-C compared
What differs1095-A1095-B1095-C
Header on the formHealth Insurance Marketplace StatementHealth CoverageEmployer-Provided Health Insurance Offer and Coverage
Who sends itA federal or state ACA Marketplace (healthcare.gov or your state exchange)An insurer, a government program (Medicare, Medicaid, CHIP, TRICARE, VA), or a small self-insured employerAn applicable large employer: 50 or more full-time employees, counting full-time equivalents
What it reportsYour Marketplace policy, month by month: premium, SLCSP benchmark, and advance premium tax creditThat you had minimum essential coverage, and for which monthsWhat coverage the employer offered you, what it cost, and why (the line 14/16 codes)
Needed to file?Yes, if advance credit was paid. It feeds Form 8962.No. Records only.No. Records only.
Attached to your return?No. Nothing in the 1095 family is attached; the A's numbers are transcribed onto Form 8962.No.No.
Still mailed automatically?Yes, by January 31.No. Furnish-on-request since the 2024 forms.No. Furnish-on-request since the 2024 forms.
If it's wrong, callThe Marketplace (1-800-318-2596 for healthcare.gov)The coverage provider on the formThe employer's benefits contact on line 10

Two details in that table are newer than most of what ranks for this search. Since the 2024 forms, the B and the C are no longer mailed automatically (details below), and the “needed to file” row carries more weight for 2026 coverage than it has in years, because the subsidy math it feeds got stricter (also below).

Which forms will you get?

Trace your coverage, not your employer size charts. Where the coverage came from decides the form; if your year had more than one source, you get more than one form.

Which 1095 you get is decided by where your coverage came fromA decision tree. The starting question is where your health coverage came from during the year. Marketplace coverage through healthcare.gov or a state exchange produces a Form 1095-A, which is needed for Form 8962 if advance credit was paid and arrives automatically by January 31. Coverage from an employer with 50 or more full-time employees produces a Form 1095-C, which is records-only and furnished on request since the 2024 forms. Coverage from an insurer directly, from a government program such as Medicare, Medicaid, CHIP, TRICARE or VA care, or from a small self-insured employer produces a Form 1095-B, also records-only and furnished on request. Coverage from more than one source in a year produces more than one form, and only the 1095-A months matter on the return.Where did your coverage come from?healthcare.gov / state exchangeemployer with 50+ full-time employeesinsurer / Medicare / Medicaid / CHIP /TRICARE / VA / small self-insured employer1095-AMarketplace StatementNeeded for Form 8962if advance credit was paidArrives automatically by Jan 311095-CEmployer offer of coverageRecords only.Nothing goes on your return.On request since the 2024 forms1095-BProof of coverageRecords only.Nothing goes on your return.On request since the 2024 formsCoverage from more than one source in a year means more than one form. Only the 1095-A months do anything on the return.Sender rules: IRS Q&A on health care information forms; furnishing rules: P.L. 118-167 (Dec 23, 2024).Granite · August 2026 · granite.co

Scroll the diagram sideways to see all of it.

The whole decision is the sender. Marketplace coverage produces the one form your return can’t do without; everything else produces paperwork you keep.

A common combination: you spent January through June on a Marketplace plan, then took a job with a large employer. You’ll get a 1095-A covering the Marketplace months, a 1095-C from the new employer, and possibly a 1095-B from the insurer behind the employer’s plan. At filing time you reconcile the 1095-A months on Form 8962 and file the other two forms in a drawer, ideally a drawer that reads them.

Do you need it to file? Only the A, and the IRS enforces it

The IRS says it plainly: you are not required to file a tax return solely because you received a 1095-B or a 1095-C, and no 1095 is attached to your return. The 1095-A is different. Not because you attach it (you don’t), but because Form 8962 is built from its Part III columns whenever advance premium tax credit was paid.

The enforcement is automatic. If IRS records show advance credit was paid on your policy and your e-filed return arrives without a Form 8962, the return is rejected under business rule F8962-070. You then refile with the form completed, or with a written explanation of why it’s absent. A paper return in the same situation is accepted and followed up by mail, which is slower in the worst way: an IRS letter instead of an instant bounce.

This is why healthcare.gov’s advice is blunt: don’t file until you have an accurate 1095-A. Waiting on a 1095-B or 1095-C, by contrast, is never a reason to delay filing.

How to read your 1095-A

The form has three parts, and only the third one does arithmetic.

  • Part I: recipient information.The Marketplace that issued the form, its policy number for your plan (the number to read off if you call them), and your coverage start and termination dates. One quirk worth knowing: there’s no EIN here, because Marketplaces aren’t employers. Our extraction schema learned that the hard way, it fingerprints a 1095-A by issuer name instead of EIN, because the EIN box that anchors most tax documents simply doesn’t exist on this one.
  • Part II: covered individuals.Everyone on the policy, with their coverage months. Check the names now: a person listed here who belongs on someone else’s tax return is how you end up in the shared-allocation rules below.
  • Part III: coverage information. Twelve monthly rows, three columns, and the only numbers on any 1095 that your return will ever use.

Counted from Granite’s document schema library on August 24, 2026: the three 1095 variants carry 19 distinct fields, and only three of them, the 1095-A’s annual premium, SLCSP, and APTC totals, ever reach a tax return. Everything on a 1095-B or 1095-C is keep-only.

The three columns of Form 1095-A Part III
ColumnWhat the form calls itWhat it actually is
Column AMonthly enrollment premiumsThe premium for your plan each month. It can legitimately differ from what you paid: it may include only essential health benefits, it's prorated for mid-month starts and ends, and pediatric dental portions can be folded in.
Column BMonthly SLCSP premiumThe second-lowest-cost Silver plan benchmark for your household. Not a bill, and not your plan. It's the yardstick your credit is computed against on Form 8962 lines 12–23.
Column CMonthly advance payment of premium tax creditThe subsidy paid directly to your insurer each month. Blank or zero if you paid full price. This is the amount you're reconciling: what was paid in advance versus what your income says you were owed.

The reading order that saves the most grief: scan column Cfirst. If it’s all zeros or blank, no advance credit was paid, you aren’t forced onto Form 8962 by rule F8962-070, and you may still choose to file it to claim the credit at tax time if your income qualifies. If column C has amounts, Form 8962 is mandatory, and columns A and B are the other two inputs to that math.

Of the 19 fields on the 1095 family, only three ever reach a tax returnA diagram of the 19 fields Granite’s schema library tracks across Forms 1095-A, 1095-B, and 1095-C: six universal fields (tax year, variant, recipient name, recipient SSN, issuer name, issuer EIN), six on the 1095-A only (policy number, coverage start and end dates, annual premium, annual SLCSP, annual advance credit), three on the 1095-B only (origin-of-coverage code, employer name, employer EIN), and four on the 1095-C only (offer-of-coverage code, employee required contribution, safe-harbor code, self-insured flag). An arrow shows that only three of the eighteen, the 1095-A annual premium, SLCSP, and advance-credit totals, flow onward to Form 8962 and from there to the Form 1040. Every field on a 1095-B or 1095-C is keep-only.19 fields across the familyOn all three forms: tax year, variant, recipient, SSN, issuer, EIN6 fields1095-A only: policy number, coverage dates, annual premium, SLCSP, APTC6 fields1095-B only: origin-of-coverage code, employer name, employer EIN3 fields1095-C only: offer code, required contribution, safe-harbor code, self-insured flag4 fields3 reach your returnpremium · SLCSP · APTC→ Form 8962 → Form 1040Every field on a 1095-B or 1095-C is keep-only. Counted from Granite’s tax/1095 extraction schema, 2026-08-24.Granite · August 2026 · granite.co

Scroll the diagram sideways to see all of it.

The 1095 family in one picture: 19 fields, 3 that matter at filing time, all three of them on the A. Counted from Granite’s document schema library on August 24, 2026.

For the document itself, what each field means, how long to keep one, what Granite extracts, the 1095-A reference page is the companion to this guide.

A worked Form 8962 example

Reconciliation is one subtraction: the credit your actual income supports, minus the advance credit that was already paid out. Positive means more refund; negative means you repay, usually up to a cap. Here is the mechanism with concrete numbers.

Say your 1095-A Part III shows, for all twelve months: column A $450(your plan’s premium), column B $520 (the SLCSP benchmark), column C $300 (advance credit paid to your insurer). Annual totals: $5,400 premium, $6,240 SLCSP, $3,600 advance credit.

  1. Form 8962 computes your allowed credit from income, not from what you received. Your household income lands at some percentage of the federal poverty line, that percentage maps to an expected contribution, and your allowed monthly credit is the column B benchmark minus that contribution (capped at your actual column A premium). Column B is only a measuring stick: you never owed $520, and nobody paid it.
  2. If the math allows more than you got, say your income came in lower than you estimated at enrollment and the allowed credit works out to $4,100. The $500 difference lands on line 26 and flows to Schedule 3 of your 1040 as net premium tax credit. It increases your refund.
  3. If the math allows less than you got, income came in higher, and the allowed credit works out to $3,000, you received $600 too much. That excess flows through lines 27–29 to Schedule 2 as excess advance premium tax credit repayment. For tax year 2025, repayment is capped by income band: a single filer between 200% and 300% of the poverty line repays at most $975no matter how large the excess, per the IRS repayment limitation table. Here the $600 sits under that cap, so you’d repay the full $600. (The complete table is below, because the cap is exactly what disappears above 400%.)

That’s the entire machine. Every troubleshooting rule on this page, wrong column A, blank column B, multiple forms, exists because one of those three inputs came in wrong or split across documents.

When the numbers look wrong (and when they only look wrong)

Column A doesn’t match what I paid

Usually it’s not an error.healthcare.gov lists three legitimate reasons the “monthly enrollment premium” differs from your bank statement: the column may include only the premium for essential health benefits (extra adult dental or vision riders are excluded), mid-month starts and ends are prorated, and a pediatric dental premium can be folded in. Compare against those three before you call the Marketplace.

Column B is zero or blank

If no advance credit was paid, a zero or blank column B is expected, and the IRS explicitly says you don’t need a corrected form. You look up your own benchmark with the healthcare.gov tax tool and use that figure on Form 8962. Column B is genuinely wrong, and worth fixing via the same tool, when it shows an amount for months where your household changed (a move, a marriage or divorce, a birth) and the Marketplace didn’t know.

Column C shows nothing, and I paid full price

Also correct. You still get a 1095-A, and if your final income qualifies, you can claim the entire credit at filing time on Form 8962, no advance payments required. People who deliberately decline the subsidy and settle up at tax time do exactly this.

More than one 1095-A, and policies shared across returns

Multiple forms are normal; a missing form is not.You get a separate 1095-A when you switched plans mid-year, when an application change (a move, an added or removed family member) created a new enrollment, when household members were on different plans, or when one plan covered more than five people and spilled onto a second form. The Form 8962 instructions tell you how to combine the columns, for full-year same-plan situations it’s addition, and the monthly rows exist for everything messier.

The genuinely tricky case is a policy shared across tax families: a divorce mid-year, or a child enrolled on your policy but claimed by your ex. The Marketplace sends the 1095-A to one taxpayer, but the 8962 instructions require both returns to allocate the policy’s columns between them, by agreement, or by default percentages when there isn’t one. If that’s your year, this is the moment this guide honestly hands you to the instructions themselves or a preparer; the allocation rules have real forks in them.

The 1095-B, decoded

The only field on a 1095-B with any decoding to do is line 8, a single letter identifying where your coverage came from. The rest of the form is names, addresses, and checked months.

The letter codes run A through G; the ones you’ll actually see are B (employer-sponsored coverage, in which case Part II names the employer), C (a government program, Medicare, Medicaid, CHIP, TRICARE, VA), and D(a plan you bought directly from an insurer in the individual market, off-exchange). Part IV’s month-by-month checkboxes are the actual payload: proof of minimum essential coverage for each month. Nothing on the form transfers to your return, but those checked months are exactly what you’d want in hand if a state coverage mandate or an eligibility question ever looks back at your year.

The 1095-C, decoded (why it looks like cipher)

A 1095-C looks unreadable because its payload is two code grids and a dollar amount, written for the IRS, not for you. Three lines carry all of it:

  • Line 14, what was offered, as a code from 1A to 1V. 1A is the “qualifying offer” shorthand: minimum-value coverage offered to you, your spouse, and dependents at low cost. 1E is the everyday version: minimum-value coverage offered to you and your family at whatever line 15 says. 1H means no offer that month.
  • Line 15, what self-only coverage would have cost you, per month. Note what this is not: it’s not what you paid, and not the family premium. It’s the cheapest self-only option’s employee share, the number the IRS uses to judge whether the offer was affordable.
  • Line 16, the employer’s explanation, codes 2A through 2H. 2A: you weren’t employed that month. 2B: not full-time. 2C: you were enrolled, the code that ends most affordability questions. The rest are affordability safe harbors and transition rules, the employer talking to the IRS over your head.

If Part III of a 1095-C lists covered individuals, the employer’s plan was self-insured, and the form is doing double duty as your proof-of-coverage record too; that’s the one case where a large employer’s form replaces the 1095-B you might otherwise expect. None of it goes on your return either way. The one number worth a second look is line 15: if it’s a surprisingly large share of your pay, that’s the thread to pull with HR, or the reason a Marketplace plan with a credit might have been the better deal, which is a conversation for open enrollment, not for filing season.

Why your B or C never arrived: furnish-on-request is the new default

Since the 2024 forms, employers and coverage providers no longer have to mail 1095-B and 1095-C statements automatically. The Paperwork Burden Reduction Act (P.L. 118-167, signed December 23, 2024) lets them post a notice and furnish the form only to people who ask. The notice has to be clear, conspicuous, reasonably accessible, and include contact details; a requested form must be furnished within 30 days of the request, or by January 31, whichever is later.

The practical translation: a missing 1095-C is now the normal case, not a payroll error. Nearly every page ranking for this search still describes the old automatic-mailing regime, because the change lives in employer-compliance alerts and never got translated for the people who used to receive the forms. Two things follow from it. First, don’t wait on a B or C to file, you never needed them for that. Second, if you want the record, and coverage records are worth having, you now have to ask for it and keep it yourself, because there won’t be a fresh copy in the mail every February. The request goes to the employer’s benefits contact or the coverage provider on the form, not the IRS.

(A second law signed the same day, the Employer Reporting Improvement Act, is why you may also be offered your form electronically with consent. Different statute, same direction: less paper arriving unbidden.)

The 400% cliff is back for 2026, which makes the 1095-A matter more

The enhanced premium tax credits Congress created in 2021 expired on December 31, 2025, and as of this writing (August 2026) no extension has become law. The House passed a three-year extension in January 2026, 230–196, but it has not advanced in the Senate. Two different rule sets now straddle the filing seasons, and it pays to know which one your 1095-A falls under.

  • Tax year 2025 (the return you file in early 2026):still the enhanced math. Contributions top out at 8.5% of income, and there is no income ceiling, the 2025 Form 8962 instructions literally say “enter 401” if your income exceeds 400% of the poverty line, and you can still be allowed a credit. Repayment of excess advance credit is capped by the table below (from Rev. Proc. 2024-40), except in the top band.
  • Tax year 2026 (filed in 2027):unless an extension passes, the pre-2021 rules return. Above 400% of the poverty line, eligibility ends, and with it the repayment cap, meaning an income estimate that drifts over the line during the year can turn every dollar of advance credit into a bill at reconciliation. If your income is anywhere near that boundary, the columns on your 2026 1095-A deserve more attention than they’ve needed in five years, and reporting income changes to the Marketplace promptly stops the excess from accumulating in the first place.
Form 8962 repayment limitation for tax year 2025, by household income as a percentage of the federal poverty line
Household income (% of poverty line)Single filer capAll other statuses
Under 200%$375$750
At least 200%, under 300%$975$1,950
At least 300%, under 400%$1,625$3,250
400% or moreNo limitNo limit

Those caps are the tax year 2025 repayment limits from the IRS’s inflation adjustment. Skip the dollar figures and read the last row: at 400% and above, the cap has never applied, and for 2026 coverage that top band is where eligibility itself now stops.

When each form arrives

The 1095-A must be furnished by January 31. The B and C deadline is March 2, 2026 for 2025 forms, but under furnish-on-request most people only ever see a notice.

  • 1095-A: the IRS instructions require Marketplaces to furnish it on or before January 31 (for 2025 coverage, January 31, 2026). healthcare.gov posts the PDF in your account between mid-January and February 1 and says to expect the mailed copy no later than mid-February, the online copy is reliably the faster one. Log in, open the coverage year’sapplication (2025, not the 2026 one you just renewed), and look under “Tax Forms.”
  • 1095-B and 1095-C: for 2025 forms, the general furnishing deadline is March 2, 2026, but under furnish-on-request most filers will only ever see a website notice. A requested copy must come within 30 days (or by January 31, whichever is later).

Sequencing your filing: the 1095-A is worth waiting for, the other two never are. If you’re assembling the whole January stack, the tax document checklist generates the full list for your situation.

Wrong or missing forms: who to call (never the IRS first)

Corrections flow from the sender.For a 1095-A that’s missing or wrong, contact the Marketplace, healthcare.gov’s call center is 1-800-318-2596, and they issue a corrected form; the IRS doesn’t fix Marketplace statements. Before calling about a “wrong” column A or B, run through the only-looks-wrong cases above, they cover most calls.

If a corrected 1095-Aarrives after you’ve filed and the changes touch your Form 8962 inputs, amend on Form 1040-X; if they don’t, keep both copies and move on. For a missing 1095-B or C, the request goes to the insurer or employer on the notice, on the 30-day clock described above.

How many people are in this

The 1095-A is not niche paperwork: 24.3 million people selected Marketplace plans for 2025, and as of February 2025, 93% of Marketplace enrollees were receiving advance premium tax credit, averaging $549.69 per month against an average full premium of $618.76, per CMS enrollment data. Every one of those subsidized households gets a 1095-A and owes the IRS a Form 8962 reconciliation.

For 2026, CMS reported 23.1 million plan selections, about 1.2 million fewer than 2025’s record, in the first open enrollment conducted as the enhanced credits expired. The forms keep coming either way; what changed is how expensive a reconciliation surprise can be for the people near the income boundary.

What to keep, and for how long

Keep the 1095-A with the return it supports, at least the IRS’s three-year limitations period, longer if you keep the return longer. Keep the B and the C as proof of coverage for the same year. The A earns its shelf space: it’s the source document behind your Form 8962 numbers if the credit is ever questioned. If one goes missing, older copies live under that year’s application in your Marketplace account.

The B and the C used to feel disposable because a fresh one arrived every February. Under furnish-on-request, the copy you keep may be the only one that exists without a written request and a 30-day wait, worth remembering the year a state coverage mandate, a Medicare enrollment, or a benefits dispute over an old EOB asks you to prove coverage for a year long past. This is exactly the paperwork pattern the January document stack is full of: forms that matter rarely, but matter completely when they do.

FAQ

1095 questions people actually ask

What is a 1095 form used for?
A 1095 documents the health coverage you had, or were offered, during the year under the Affordable Care Act. There are three versions, split by who sends them: the 1095-A comes from a Health Insurance Marketplace, the 1095-B from an insurance company or a government program like Medicaid or CHIP, and the 1095-C from an employer with 50 or more full-time employees. Only the 1095-A is used to prepare your return, because its numbers feed Form 8962, where you reconcile the premium tax credit. The B and the C are records to keep, not forms to file.
What is the difference between 1095-A, 1095-B, and 1095-C?
The sender, and what you have to do with it. A 1095-A comes from a federal or state ACA Marketplace and you need it to complete Form 8962 on your tax return. A 1095-B comes from a coverage provider, an insurer, a government program such as Medicare or Medicaid, or a small self-insured employer, and simply documents that you had minimum essential coverage. A 1095-C comes from an applicable large employer, one with 50 or more full-time employees, and documents what coverage the employer offered you. Neither the B nor the C gets attached to your return or entered on it.
Do I need my 1095-B or 1095-C to file my taxes?
No. The IRS says directly that you are not required to file a tax return solely because you received a Form 1095-B or 1095-C, and neither form is attached to your return. You do not wait for them and you do not enter them anywhere. Keep them with your tax records as proof of coverage. The one 1095 that can hold up your filing is the 1095-A, because its figures are required on Form 8962 whenever advance premium tax credit was paid.
Do I need my 1095-A to file taxes?
Yes, if you had Marketplace coverage. Form 8962 is built from the monthly premium, SLCSP, and advance-credit columns in Part III of your 1095-A. If advance premium tax credit was paid and your e-filed return has no Form 8962, the IRS rejects it under business rule F8962-070 and you have to refile with the form or a written explanation. Healthcare.gov's own instruction is blunt: don't file your taxes until you have an accurate 1095-A.
Why did I get more than one 1095-A?
Because something about your enrollment changed. Switching plans mid-year, reporting a move, adding or removing a family member, or having household members on different plans each produces a separate form, and a plan covering more than five people spills onto an extra form as well. Nothing is wrong. You use all of them: the Form 8962 instructions tell you how to combine the monthly columns when more than one form covers the year.
Why is column B of my 1095-A zero or blank?
Column B is the second-lowest-cost Silver plan premium, the benchmark your credit is computed against. When no advance credit was paid on your policy, the Marketplace often leaves the column at zero or blank, and the IRS instructions say you do not need a corrected form. You look up the correct benchmark yourself with the tax tool at healthcare.gov/tax-tool and use that figure on Form 8962. Column B is also wrong if it shows an amount for a month you had a life change the Marketplace didn't know about, a move, a marriage, a birth.
What happened to my 1095-C? My employer used to send one every year.
The law changed. Under the Paperwork Burden Reduction Act, signed December 23, 2024, employers and coverage providers no longer have to mail 1095-B and 1095-C statements automatically. They can instead post a notice that the form is available on request. If you want your copy, ask for it: the employer must furnish it within 30 days of your request, or by January 31, whichever is later. Since the form is records-only, most people never notice the difference at filing time.
I already filed, and then a corrected 1095-A arrived. What now?
Compare the corrected form against the one you used. If the changed figures affect Form 8962, premiums, SLCSP, or advance credit amounts, you generally need to amend your return on Form 1040-X so the reconciliation matches the Marketplace's corrected numbers. If the correction doesn't change your 8962 math, keep both forms with the return and do nothing. A corrected form is marked 'Corrected', so there's no ambiguity about which one governs.
Where do I find my 1095-A online?
In the Marketplace account you enrolled through, not at the IRS. On healthcare.gov, log in, open the application for the coverage year, in early 2026 that means your 2025 application, not 2026, and look under Tax Forms for the PDF. State exchanges have equivalent screens. Forms are posted between mid-January and February 1, usually weeks before the paper copy arrives. For an earlier year, open that year's application the same way.
Can I get a 1095-A, a 1095-B, and a 1095-C in the same year?
Yes, and it's common when your coverage changed. Half a year on a Marketplace plan, then a new job with a large employer, produces a 1095-A for the Marketplace months, a 1095-C from the employer, and possibly a 1095-B from the insurer behind the employer's plan. Only the 1095-A does anything on your return, and only for the months it covers. The others are records.
What is the second-lowest-cost Silver plan (SLCSP)?
It's the benchmark the premium tax credit is measured against: the second-cheapest Silver-tier plan available to your household through your Marketplace. You never had to buy it, your actual plan can be Bronze or Gold, but your credit is computed as the SLCSP premium minus your expected contribution based on income. That's why column B of the 1095-A exists, and why a wrong or blank column B changes your refund math even though it isn't a bill for anything.
How long should I keep 1095 forms?
Keep a 1095-A as long as you keep the return it supports, at least three years, the IRS's general period of limitations, and longer if you're conservative, because it's the source document behind your Form 8962 credit. Keep 1095-B and 1095-C forms with the same year's records as proof you had, or were offered, coverage. Now that B and C are furnish-on-request, the copy you saved may be the only one you can put your hands on quickly years later.

Keep every 1095 where you can actually find it

Drop a 1095 into Granite and it reads the header, works out whether it's an A, a B, or a C, pulls the tax year, the issuer, and, on an A, the premium, SLCSP, and advance-credit totals that Form 8962 needs, then files it into that year's tax collection next to your W-2 and 1099s. Now that the B and the C only arrive if you ask, the copy you keep is the copy that exists.