Start with the exact basis entry

Pull the form itself, not the summary email your broker sent with it. What you need from one row is small: the tax year printed on the form, the number (or the empty space) in Box 1g, and whether Box 9 is checked on that same row.

Box 1g is the basis field; Box 9 is the noncovered indicator. The IRS Instructions for Form 1099-DA (2026) attach two different conditions to what can sit in Box 1g. A broker may leave it blank when the asset is noncovered, Box 9 is checked, and the broker chooses not to report basis.

The broker enters -0- there only when the asset sold actually had zero basis. Those are separate statements about your sale, and the difference decides your next move.

A blank box does not establish zero tax basis. Under the recipient instructions, the taxpayer determines basis from their own records, so a missing number is a gap in what the broker reported, not a finding about what you paid. If more of this season's form questions are open, you can also explore the 1099-DA guide index.

What you see What the entry says What to check Next action
Box 1g empty Basis was not reported for this row, which the instructions permit for a noncovered asset with Box 9 checked Your own acquisition record for that asset: the date and what you paid Determine basis from your records and keep them filed beside the form
Box 1g shows -0- The broker is reporting that the asset sold had zero basis Whether your records actually support a zero cost If your records show a purchase price, keep that evidence and ask the issuer about the entry

Check each row before drawing a conclusion

A first-season statement often carries all three states at once: one row with nothing in Box 1g, one with a literal -0-, and one with a figure that looks plausible. The statement as a whole tells you almost nothing. Each row was reported under its own facts, and each row gets its own check.

We compared the dated box instructions against what readers describe seeing in those fields, and the failure mode is consistent: a blank field gets copied into a worksheet as a zero because the column needed a number.

Suppose you do that with a coin you bought years ago and still have the exchange confirmation for. Nothing on the form changed, but your own calculation just discarded a documented cost. That is the mistake this section exists to prevent.

Bookkeeping habits are behind the emphasis here. A figure on a statement is a claim until a source record backs it, and that applies to a populated Box 1g as much as to an empty one. A number's presence says the broker had something in its system, not that the something matches your purchase.

The branches below are an editorial reading aid built from the box rules in the 2026 instructions. The labels describe row states you might see; they are not a reproduction of any broker's layout.

Row-state decision tree

Start: pick one affected row. Note the tax year on the form and whether Box 9 is checked for that row.

  • Box 1g blank → read it as "not reported," check coverage for that asset (when you acquired it, and whether you bought it inside this broker's account) → locate the purchase evidence → carry your documented basis forward.
  • Box 1g shows -0- → compare against your acquisition evidence. Records support a zero cost: file the record with the form. Records show a purchase price: keep the evidence and identify the discrepancy for the issuer.
  • Box 1g shows a number → compare it with your documented acquisition record. It matches: this row is done. It differs: keep both figures and work out which acquisition the issuer used.

Repeat for the next affected row. The outputs are records to gather or a question to ask the issuer, not a tax determination.

Does this sale involve a covered asset?

January 1, 2026 is the acquisition-date cutoff (current figure at the IRS). An asset you acquired before 2026 is noncovered. An asset acquired in 2026 or later can be covered, but only when you acquired it in the broker's own custodial account and held it there through disposition.

An asset transferred into that account is noncovered, whenever you bought it.

So the purchase date alone does not answer the question.

Buying in March 2026 and moving the coin to a second platform before selling produces a noncovered sale at the second platform, because the acquisition did not happen in that account and the holding was not continuous there.

Two things have to line up: where the asset was acquired, and whether it stayed put.

That is also why the receiving broker has no purchase price to report. It received an incoming balance, not a trade record with a date and an amount, and nothing in a transfer obliges the sending platform to hand over that history. For the mechanics of what travels and what does not, see why a wallet transfer can leave the broker without your purchase history.

Worth checking the cutoff and the custody conditions against the official instructions for the filing year you are actually working on, since the form and its instructions are revised by year. The version cited on this page is the 2026 revision, which is the one that governs sales reported for tax year 2026.

For your row-by-row pass, coverage matters for one reason: it explains a blank Box 1g without excusing you from producing a basis figure.

What changed between tax years 2025 and 2026?

For tax year 2025, brokers must report gross proceeds on Form 1099-DA, and basis reporting is optional. That is the source of most blank fields on a first-season form. It does not mean brokers were barred from supplying basis; some did, which is why a 2025 form can carry a populated Box 1g that still deserves a comparison against your record.

From tax year 2026 onward, brokers must also report basis for covered digital assets. Basis stays optional for noncovered assets, and the optional reporting methods available for qualifying stablecoins and specified NFTs can leave basis out even after 2025.

Which answers the next-year question directly: no, the phase-in does not guarantee a complete form in 2027. Every pre-2026 purchase you still hold is noncovered, every transferred-in position is noncovered, and noncovered basis reporting remains optional. Plan on keeping your acquisition records for as long as you hold the assets.

The rule behind all of this is Treasury Decision 10000, published July 9, 2024, which the IRS Form 1099-DA instructions point to for further guidance on the broker reporting regulations.

Does missing basis make the full proceeds taxable?

No. The recipient instructions put the determination on the taxpayer: where the broker has not reported basis, you determine and report accurate basis from your own books and records, and the blank field does not settle the gain by itself.

The consequence is arithmetical, not automatic. If you enter zero where documented positive basis exists, you remove the subtraction and report more gain than the transaction produced. That overstatement comes from your worksheet, not from the form.

The reverse also holds: an unsupported number you wish were true is not basis either.

Myth versus fact

  • "Blank means my cost was zero." The instructions treat the two differently: blank means not reported, and -0- is reserved for an asset that actually had zero basis.
  • "Everything I bought in 2026 is covered." The acquisition date is one condition. Acquisition inside the broker's custodial account and continuous holding there also have to hold.
  • "Next year's form will show every basis figure." Basis for noncovered assets remains optional, and the specified optional reporting methods can omit it as well.

Choose the next step for the affected row

Each branch has a real endpoint, and only one of them involves contacting anyone.

Blank Box 1g: find the purchase evidence and treat the strongest record as your basis support.

Exchange trade confirmations and dated account statements sit above a screenshot or a spreadsheet you typed from memory, and a bank or card record of the funding transfer helps when the trade record is gone.

That is a whole workflow of its own, so rebuild your cost basis from the records you still have when the evidence is thin.

Explicit -0- that your records contradict: this is the issuer question. Write down the row, the proceeds figure, the date of sale, and the acquisition record you hold, then ask the broker what acquisition the entry reflects and whether it will correct the form. A corrected form from the broker and the basis you report on your own return are two separate things; you may end up with the second and not the first.

Populated figure that differs from your record: keep both, work out which lot or acquisition the broker used, and decide which figure your evidence supports before anything goes on a return.

Once your rows have documented support, you can compare your 1099-DA basis rows with your documented records. A comparison tool sorts matches from mismatches. It cannot create basis that no record supports.

Two cautions that save trouble later. Do not invent a figure to fill a column, and do not leave a sale off because its records are missing; a documented estimate and an omission are not in the same category. Keep original documents as they are, and if you assemble a reconstruction, date it honestly for when you built it rather than backdating it to the trade.

Where a disposition is disputed, the custody path runs through several platforms and wallets, or an unresolved gap is large enough to move real money, take that row to a tax professional who can look at your actual transactions.

Choose one affected row, keep its form entry beside the supporting records, and rebuild your cost basis from the records you still have.

Sources

  • IRS, Instructions for Form 1099-DA (2026) - Covered security, Noncovered security, and Box 1g: the acquisition cutoff, the custody conditions, and when a broker may leave Box 1g blank or must enter -0-. irs.gov/instructions/i1099da (retrieved September 26, 2026)
  • IRS, Instructions for Form 1099-DA (PDF) - the reporting phase-in and the scope of the optional reporting methods, distinguishing tax year 2025 from tax year 2026 onward. irs.gov/pub/irs-pdf/i1099da.pdf (retrieved September 26, 2026)
  • IRS, Form 1099-DA recipient instructions - the taxpayer's responsibility to determine basis when the broker has not reported it; 2026 revision context. irs.gov/pub/irs-access/f1099da_accessible.pdf
  • IRS, Reminders for Taxpayers About Digital Assets - supporting reporting-year context for the 2026 season. irs.gov/newsroom/reminders-for-taxpayers-about-digital-assets
  • Treasury Decision 10000, 89 FR 56480 - the underlying broker reporting rule on gross proceeds and basis, published July 9, 2024. federalregister.gov