Your Coinbase 1099-DA, and what it gets wrong
Coinbase issues Form 1099-DA to US customers starting with the 2025 tax year, reporting gross proceeds only for 2025 (cost basis is added from tax year 2026), and separately issues Form 1099-MISC to US customers who earned $600 or more in rewards or staking income; Coinbase states it does not issue Form 1099-K.
The form is accurate about what Coinbase could see. It is silent about everything it could not — which, for most people, is where the cost of their coins lives.
What goes wrong specifically on Coinbase
Convert is the classic mismatch: on the form it is a sale, and the coin you received arrives with no basis of its own unless you prove what the leg was worth.
Rewards and staking income are reported on a 1099-MISC, not on the 1099-DA — so income already taxed once is invisible to the form that later reports the sale, which is how the same coins get taxed twice.
Anything you sent in from another exchange or a wallet is noncovered by definition, so box 1g is blank and the whole sale price reads as gain.
The blank you are looking at
Box 1g is empty because Coinbase was never required to fill it in for coins it did not sell you — anything moved in from another exchange or a wallet is noncovered, and its cost is yours to prove.
BOX 9 -- printed caption 'Check if digital asset is a noncovered security'. When box 9 is checked, the broker need not complete boxes 1d, 1g, 1h, 1i, and 6 and need not check box 2, and the recipient instructions on the form itself say boxes 1d, 1g, 1h, 1i, 2, and 6 may be blank. Box 2 ('Check if basis reported to IRS') is the confirming signal in the other direction: if box 2 is unchecked, whatever is (or is not) in box 1g was not reported to the IRS.
Two separate mechanics. (1) DISCLOSURE: if any of the units sold had been transferred into the broker's custodial account from somewhere else, the broker reports the number of those units in BOX 12a (to 18 decimal places) and the date they arrived in BOX 12b, in MM/DD/YYYY; box 12b is left blank if the units came in on a variety of dates. This is required for sales effected in 2025 and for sales effected after 2025. (2) STATUS AND BASIS: a digital asset that was transferred in to the broker providing custodial services is expressly listed in the instructions as a NONCOVERED security.
Putting the right number on your return
The IRS mechanism turns on ONE question: was the basis reported to the IRS? (1) BASIS WAS REPORTED TO THE IRS (box 2 checked; Form 8949 box G or J): you must enter in column (e) the basis exactly as shown in box 1g -- even though you know it is wrong -- enter code B in column (f), and correct the error with an adjustment in column (g), computed with the 'Worksheet for Basis Adjustments in Column (g)'. That worksheet: line 1 = basis shown on the 1099-DA, line 2 = the correct basis; if line 1 is larger, enter the difference in column (g) as a POSITIVE number (it increases gain); if line 2 is larger, enter the difference in column (g) as a NEGATIVE number in parentheses (it decreases gain). The Note printed on Form 8949 itself says the same thing: 'If you checked Box A or Box G above but the basis reported to the IRS was incorrect, enter in column (e) the basis as reported to the IRS, and enter an adjustment in column (g) to correct the basis.' (2) BASIS WAS NOT REPORTED TO THE IRS, OR BOX 1g IS BLANK (box 2 unchecked, box 9 checked; Form 8949 box H or K, or box I/L if no form was issued at all): you simply enter the CORRECT basis directly in column (e) and enter -0- in column (g) -- no adjustment mechanics, and the worksheet is not needed. The 8949 instructions phrase it as: 'For noncovered securities, enter the correct basis of the property in column (e) if: No basis is shown on Form 1099-B or Form 1099-DA (or substitute statement), or The basis shown wasn't reported to the IRS.' This is the answer for almost every tax year 2025 Form 1099-DA, because 2025 basis reporting was voluntary. The form's own Instructions for Recipient say it plainly: 'If box 1g is blank, you will need to determine your basis based on your own books and records.' Note also that if box 1g shows any entry INCLUDING ZERO, that figure was reported to the IRS as basis -- a printed -0- is a reported number, not a blank, and correcting it requires the code B route. Proceeds in column (d) are always reported as shown on the form regardless.
Digital-asset rows use Form 8949 boxes G–L, never the securities boxes A–F — the instructions say so explicitly, and our exports follow them.
Find out what yours overstates
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1099da-2026.1 · reviewed Aug 2026 · ClearBasis is tax software, not a law firm, accounting firm or tax preparer; information, not advice. Coinbase is a trademark of its owner; no affiliation is implied.