MundoKit

Form 1099-DA cost-basis reconciliation worksheet

Enter 2026 digital-asset sales using the CSV schema. Compare reported basis with your records and calculate gains only for rows with a known basis.

A private manual CSV worksheet for 2026 sales. It keeps unknown basis separate from zero basis. Enable JavaScript to reconcile records.

Last checked 2026-11-14. Rules change, sometimes at short notice. We list the date we last checked each official source; confirm with the official government source before you travel, buy or file. This is general information, not legal or immigration advice.

This is a general estimate for information only, not tax, legal or financial advice. Real rules have more conditions than a calculator can show, so check the official source below or a qualified professional for your situation.

How it works

For optional-method qualifying stablecoin or specified NFT statements, use the extended header id,asset,sold,proceeds,reported_basis,records_basis,basis_reported,row_type,tax_year. Enter aggregate as row_type and 2026 as tax_year. Copy box 1f proceeds, leave sold blank when box 1e is blank, and leave unknown basis blank. For example: a,Stablecoin,,12000,,,no,aggregate,2026 retains $12,000 unresolved proceeds. Do not duplicate the underlying sales. Individual sales use sale with a real sale date. The original seven-column schema remains accepted for individual sales. See IRS instructions, Box 1e.

Records basis, when entered, overrides reported basis and any difference is flagged. Otherwise reported basis is used. Blank basis stays unresolved. Known-row gain equals proceeds minus the supplied basis, before tax adjustments. Sum known-row gains without treating unresolved proceeds as gains. Displays round to cents; intermediate values are unrounded.

known-row gain = proceeds − supplied adjusted basis

Enter proceeds after applicable transaction costs and adjusted basis in USD. Do not subtract fees twice. This does not reconstruct lots, select accounting methods, assign holding periods, handle wash-sale adjustments or produce Form 8949. No wallets or accounts are connected. Maximum 1,000 rows and 500,000 bytes; quoted commas are supported, multiline cells are not.

Worked examples

One resolved and one missing basis

Proceeds $1,200 with records basis $800 give $400 known gain. A second $600 sale with blank basis stays unresolved. Total proceeds are $1,800, including $600 unresolved.

Records disagree with the broker

Proceeds $600, reported basis $900 and records basis $1,000 give a −$400 pre-adjustment loss and a mismatch flag. A statement total of $650 gives a −$50 proceeds difference.

Frequently asked questions

Is missing basis the same as zero?
No. Leave unknown amounts blank. Enter 0 only for an actual zero basis; the worksheet can then calculate that row’s gain.
Why might basis be missing in 2026?
Basis reporting is required for covered securities. Noncovered assets, including assets acquired before 2026 or transferred in, may lack reported basis. Optional reporting methods also have exceptions.
What do the two basis columns mean?
reported_basis holds box 1g. records_basis holds your supported adjusted basis. A mismatch needs review; the tool does not decide which record is legally correct.
What is basis_reported?
Enter yes or no from box 2. It records whether basis was reported to the IRS, independently of whether you supply personal records.
Can I upload a broker’s CSV directly?
Only if it matches the displayed schema exactly. Map columns first. Use a unique row ID to catch accidental duplicate IDs; different IDs can still conceal duplicate transactions.
Is the result my taxable gain?
It is an arithmetic subtotal before adjustments. Missing rows and special tax treatments require review. The CSV export is a review worksheet, not a tax filing.

Sources

Last reviewed 2026-11-14; next review due by 2027-01-15. The method is written out above so you can check our math.