Missing cost basis records is one of the most common - and most expensive - crypto tax problems. If you are facing cost basis unknown crypto irs, the stakes are high but the problem is solvable.
What the IRS Assumes
When you report crypto sales without cost basis, or when a 1099-DA shows proceeds with no corresponding cost basis on your return, the IRS may assume your cost basis is zero. On a $100,000 sale, that means $100,000 in taxable gains instead of whatever your actual gains were. This is almost certainly wrong, and you have the right to prove your actual basis.
Reconstruction Resources
Exchange transaction histories are your primary source. Most major exchanges retain records for several years and provide downloadable CSV files. Blockchain explorer tools can trace every transaction for a given wallet address. Bank statements show fiat deposits to exchanges. Credit card records show purchases. Each data source fills part of the picture.
When Exchanges Are Gone
If an exchange has closed, been hacked, or left the US market, your records may seem lost. But blockchain data persists. If you know your wallet addresses or can identify your exchange deposit addresses, a crypto tax professional can reconstruct your transaction history from on-chain data. The process is technical but well-established.
Establishing Reasonable Basis
If records are genuinely unavailable, you can establish a reasonable cost basis position using available evidence. Historical price data, the timing of your entry into crypto, your general trading patterns, and any partial records all contribute to building a defensible position. The key word is "defensible" - whatever basis you claim must be supportable if challenged.
Frequently Asked Questions
What cost basis method should I use?
FIFO sells oldest coins first, LIFO sells newest first, and specific identification lets you choose. Each produces different tax outcomes. Once chosen, the method should be applied consistently. Consult a tax professional for the optimal choice.
How is cost basis calculated for gifted crypto?
You generally inherit the donor cost basis. If you sell at a gain, use the donor basis. If you sell at a loss, use the lesser of donor basis or fair market value at the time of the gift.
What is the cost basis for airdropped crypto?
The cost basis for airdropped tokens is the fair market value at the time of receipt - the same amount you report as income. This becomes your basis for calculating gain or loss when you sell.
Get Crypto Tax Help Now
Dealing with cost basis unknown crypto irs can feel overwhelming, but there are options. Call the Law Offices of Darrin T. Mish, P.A. at (813) 229-7100 for a free consultation. We have resolved over $100 million in IRS tax debt.