Is blank cost basis on Form 1099-DA the same as zero?
No. A blank box 1g is not the same as a reported $0. Blank means the broker did not report cost or other basis to the IRS (often a noncovered security with box 9 checked, or an optional reporting method that omits basis). Entering -0- (or any other amount) in box 1g means the broker asserted that figure as basis and that information was reported. Those two states drive different Form 8949 checkboxes and different dispute paths when your records disagree.
Key takeaways
- 2026 Instructions for Form 1099-DA, box 1g: if box 9 is checked and the broker is not reporting basis, leave box 1g blank; enter -0- only if the digital asset sold actually had a basis of zero.
- Recipient Form 1099-DA language: if box 1g is blank, determine basis from your own books and records; if box 1g has any entry, including zero, that information has been reported to the IRS as basis.
- Blank basis maps to Form 8949 box H (short-term) or K (long-term): 1099-DA received, basis not reported to the IRS. Details on reconstruction: Why does my 1099-DA show no cost basis?.
- Reported $0 (or any reported figure you believe is wrong) is the basis-reported path (often G/J). Correct it with Form 8949 adjustment columns and/or a corrected form from the issuer, not by treating the box as empty.
- Blank is common for noncovered lots: units acquired before 2026, and units transferred into the broker.
- We classify hashes that set acquisition facts. We do not fill box 1g and we do not compute basis.
What blank box 1g means
Brokers report gross proceeds on Form 1099-DA for sales effected on or after January 1, 2025. Basis is mandatory for covered securities (units acquired in that broker's custody on or after January 1, 2026 and held there continuously until disposition), and voluntary for noncovered securities when the broker checks box 9. The 2026 instructions state that if the broker checks box 9 for a noncovered sale, the broker does not have to complete boxes 1d, 1g, 1h, 1i, and 6, and does not have to check box 2. Optional reporting methods for qualifying stablecoins and specified NFTs may also leave box 1g blank even when units would otherwise be covered.
Blank is therefore a reporting state: basis was not furnished on this information return, not a finding that cost was zero. Understanding your Form 1099-DA tells recipients to use the form and other records, and to calculate basis before filing. That instruction exists because the form often does not supply basis.
Common reasons box 1g is empty:
- 2025 sales, when basis reporting was not required (proceeds-only year for most brokers).
- Noncovered lots: acquired before 2026, transferred into the broker, or otherwise outside covered status, with box 9 checked and basis omitted.
- Optional stablecoin / specified-NFT reporting methods that permit omitting basis amounts.
None of those mean the taxpayer's adjusted basis is zero. They mean the §6045 return left the field for your records.
What a reported $0 means
The instructions are explicit: enter -0- in box 1g only if the digital asset sold actually had a basis of zero. The recipient form adds that any entry in box 1g, including zero, has been reported to the IRS as basis.
So a printed $0 (or -0-) is an affirmative broker assertion that adjusted basis was zero, and that assertion went to the IRS. It is not a synonym for an unknown basis. Treat it like any other reported basis figure: verify against books, keep evidence, and if it is wrong, request a corrected Form 1099-DA from the issuer and use Form 8949's adjustment mechanics rather than silently overwriting a blank.
Zero basis can be factually correct in narrow cases (for example, certain income inclusions that set basis at amounts already recognized, or other facts that truly drive adjusted basis to zero). The point is procedural: reported zero is a claimed number; blank is an omitted number.
Form 8949 paths (blank vs reported)
| Box 1g on Form 1099-DA | What the IRS was told about basis | Typical Form 8949 digital-asset checkbox | Taxpayer basis source |
|---|---|---|---|
| Blank | Basis not reported | H (short-term) or K (long-term); Y if holding period unknown on the form | Your books and records (wallet history, acquisition hashes) |
| $0 or any other amount | That amount reported as basis | G (short-term) or J (long-term) when basis was reported | Start from the form; correct with columns (f)/(g) and/or a corrected 1099-DA if wrong |
The Form 1099-DA applicable checkbox on Form 8949 codes track the same split: G/J when cost or other basis is being reported to the IRS; H/K when it is not; Y when the filer cannot tell short-term from long-term.
If you received a Form 1099-DA with incorrect information, including a wrong basis figure, Understanding your Form 1099-DA says to request a corrected form from the issuer, keep correspondence, not contact the IRS to fix the issuer's return, and not wait to file. Blank basis is not incorrect information by itself when noncovered rules allow omission; it is an incomplete input you finish from records.
Deeper reconstruction (per-wallet lots, specific identification, Notice 2026-20 relief pointers) stays on Why does my 1099-DA show no cost basis?. This page only separates blank from zero.
Classification framing: blank is not a treatment
Box 1g blank answers a broker-reporting question. It does not classify the acquisition that created the lot.
- A purchase, a taxable swap into the asset, a reward or airdrop taken into income, or a transfer-in that carries basis all set different acquisition facts. Those facts live on hashes and wallet history.
- DeFi and self-custody activity that never hits a custodial broker produces no 1099-DA at all; blank versus zero never arises. See Does Form 1099-DA cover DeFi and self-custody wallets?.
- Covered versus noncovered is why blank appears on transfer-in and pre-2026 lots even for 2026 sales. Units acquired in that broker's custody on or after January 1, 2026 and held there continuously are the covered set; transferred-in units stay noncovered.
Standard practice: hash in for what the acquisition was; use the form for what the broker reported; do not collapse blank into $0 inside portfolio software to force a gain figure.
How CryptoTaxEdge fits
Classification is a hash in, a record out. POST https://app.cryptotaxedge.com/v1/classify with { "chain", "hash" }. One category, one treatment from the closed enum (disposal, income, non_taxable, expense, needs_review), confidence 0 to 100 as a routing signal, needs_review: true and taxable: null when a treatment cannot be honestly asserted. Confidence is not an accuracy percentage.
When box 1g is blank, the firm still needs typed acquisitions behind the sold units: which hop opened the lot, whether a transfer carried basis, whether a reward created income basis. We type those events. We do not write a number into box 1g, and we do not decide whether a broker's reported $0 was correct.
Worked example
Blank, not zero. In February 2026 a client transfers 3.00000000 ETH from self-custody into a U.S. custodial exchange, then sells those 3 ETH in October 2026 for $9,000 cash. The units are noncovered (transferred in). The 2026 Form 1099-DA checks box 9, reports $9,000 in box 1f, and leaves box 1g blank. The client's true basis from prior purchases (reconstructed from classified wallet history) is $4,200.
Do not treat blank as $0 and report $9,000 of gain. Report proceeds from the form, basis $4,200 from records, on Form 8949 with box K or H as holding period requires (basis not reported to the IRS). Classify the original acquisition hashes and the transfer-in so the lot story holds; the blank box is expected, not a zero-cost assertion.
Reported zero. Same sale facts, but the broker (incorrectly) enters -0- in box 1g and checks box 2 (basis reported to IRS). The IRS was told basis was zero. That is not the blank path. Verify against records ($4,200), request a corrected Form 1099-DA from the issuer, and use Form 8949 adjustments so the return does not silently adopt $0. Do not wait to file while the correction is pending.
Two rows that look similar on a PDF viewer are different information-return states.
What CryptoTaxEdge does not do on this page
- We do not decide whether a broker correctly left box 1g blank or correctly entered -0-.
- We do not amend Form 1099-DA or populate Form 8949 columns.
- We do not compute adjusted basis, gain, or loss.
- We do not treat blank basis, or a missing form, as evidence of non-taxability.
- We do not connect to wallets or take custody. Hash in; category, treatment, confidence, and review flag out.
Classify a transaction at https://cryptotaxedge.com/explorer?src=answers. Enter a hash; ten a day, no signup.
Frequently asked questions
If box 1g is blank, is my cost basis zero for tax purposes?
No. Blank means basis was not reported on that Form 1099-DA. Determine adjusted basis from your books and records, then report it on Form 8949. The recipient form text says exactly that.
The broker put $0 in box 1g. Can I ignore it and use my own basis quietly?
Not as if the box were blank. A $0 entry was reported to the IRS as basis. If your records support a different figure, request a corrected form from the issuer and use the Form 8949 adjustment rules for incorrect basis. Keep the evidence. Do not wait to file.
Does box 9 being checked mean basis is always blank?
Often, but not always. With box 9 checked, the broker may omit basis fields, or may report basis voluntarily. Voluntary figures on a noncovered row still count as reported amounts if box 1g is filled. Blank remains the not-reported state; a filled $0 remains an asserted zero.
Where do I put a blank-basis 1099-DA row on Form 8949?
Generally box H (short-term) or box K (long-term): Form 1099-DA received, basis not reported to the IRS. Proceeds from box 1f; basis and acquisition date from your records. Full reconstruction workflow: Why does my 1099-DA show no cost basis?.
Does CryptoTaxEdge fill in blank cost basis?
No. We classify the on-chain events that explain how a lot arose. Basis arithmetic and Form 8949 preparation stay with the firm and portfolio software.
Accounting firm with crypto clients? See the Firm plan.
This is informational only, not tax advice; verify with a qualified tax professional before filing.