BasisRestore

Coinbase records

Coinbase missing cost basis: what to collect before a review

A missing cost-basis field is an evidence problem first. It does not, by itself, decide whether a transaction was taxable or how an accountant should file it.

For People and accountants working through incomplete Coinbase records. · Updated 2026-08-03

What “missing basis” actually means

Cost basis is the acquisition-side evidence attached to an asset lot. When an exchange cannot match a later sale or conversion to that evidence, the record may show an unknown or estimated basis. A zero or estimated value is a gap to investigate, not a conclusion to copy into a return.

The useful question is: which source can prove when the units arrived, how many arrived, and what acquisition evidence exists? That keeps the review separate from tax advice.

Collect the source records first

Start with original exports and statements. Keep the files unchanged and record where each file came from before making a working copy.

  • Coinbase transaction history or account statement export for the relevant date range.
  • Purchase, deposit, and transfer records that may establish the opening lot.
  • A matching record from another exchange or wallet when the asset moved before the sale.
  • The account timezone, currency, and date range used for every export.
  • A short note for anything you cannot obtain, including the attempted source and date.

Use a review sequence that preserves uncertainty

A defensible reconstruction makes each assumption visible. It should be possible for an accountant to trace a row back to its source without guessing which numbers were invented or rounded.

  1. 01Preserve the original export and calculate a file hash for the working case record.
  2. 02Normalize timestamps and asset symbols without changing the original values.
  3. 03Match deposits, withdrawals, and internal transfers before treating a movement as a disposition.
  4. 04Link a sale or conversion to the best-supported opening lot and record the evidence used.
  5. 05Leave an open item when the evidence cannot support a match; do not silently fill it with a zero basis.

Where BasisRestore fits

BasisRestore can review a qualified case using supported Coinbase records, public wallet activity, and documented manual opening lots. The output is a traceable Evidence Pack: reconciled ledger, source map, decision log, and open-items list.

The public qualification form collects metadata only. If a case fits, evidence collection happens through a separate private process. BasisRestore does not request seed phrases, private keys, exchange passwords, or withdrawal-enabled API credentials.

Sources and boundaries

These links are source context, not a substitute for advice from a licensed tax or accounting professional. BasisRestore reconciles records and documents evidence; it does not decide filing treatment.