WOYALE.
To deduct a gambling loss you have to prove it, and the IRS says how: keep an accurate diary or similar record of your winnings and losses, backed by documents. That is the rule in IRS Publication 529 and Topic 419. Crypto adds a second job. You also have to prove the dollar value of every coin you received or spent, because the tax math depends on it.
This is general information, not tax advice. A CPA can tell you what level of detail your situation calls for.
What the IRS asks for
Publication 529 says your diary should show, for each wager or session:
- when you bet and what kind of bet or game it was,
- where you bet: the venue or site and its address,
- who was with you, if anyone, and
- how much you won or lost.
It also lists other documents that help: Form W-2G, wagering tickets, canceled checks, credit records, and statements from the establishment. An IRS Chief Counsel memo (AM2008-011) points to Internal Revenue Code section 6001 and Revenue Procedure 77-29 as the basis for substantiating wagering gains and losses. For online betting, the “establishment” is the platform. Write down its name and web address, and the legal entity name from its terms.
Two rules of thumb that follow from this:
- Write it when it happens. A log rebuilt from memory in April is weak evidence. A log made at the time is stronger.
- Totals alone don’t work. “Lost about $4,000 last year” is not a record. Session-by-session entries are.
Crypto-specific records
The IRS FAQs on virtual currency say income is measured in US dollars at the time you receive the coins, and that you must keep records of the fair market value of digital assets received as income. For each crypto movement tied to betting, log:
| Field | Why it matters |
|---|---|
| Date and time (with time zone, ideally UTC) | Sets the valuation moment and the holding period |
| Transaction hash | Lets anyone confirm the transfer on a block explorer |
| Network (Ethereum, Tron, Bitcoin and so on) | The hash means nothing without it |
| Your wallet address and the platform’s address | Shows the money came from and went to you |
| Asset and quantity | The exact coin and amount, to the last decimal |
| US dollar value, and where you got it | Your income, basis or proceeds. Note the price source |
| Network fee paid | Can matter for basis and disposals; ask your preparer |
| What it was | Deposit, bet stake, payout, withdrawal, or sale |
For on-chain transfers, the IRS says the time the transaction is recorded on the ledger is the time of receipt, and it accepts a blockchain explorer’s value for peer-to-peer transfers. For exchange activity, the exchange’s recorded dollar amount is the figure to use. Either way, save evidence of the number you used.
Sample log
| Date (UTC) | Platform and type | Wager | Result | Coin and amount | USD value | Tx hash (first and last 6) | Notes |
|---|---|---|---|---|---|---|---|
| 2026-10-03 | Platform A, NFL moneyline | $100 stake | Won | 0.5 ETH received | $1,500 | 0x4f9a1c…b7e210 | ETH at $3,000, price source saved |
| 2026-10-04 | Platform A, NBA total | $50 stake | Lost | 50 USDT staked | $50 | 0x9d02ee…41ac88 | Stake debited from balance |
| 2026-10-09 | Platform A, soccer spread | $75 stake | Lost | 75 USDT staked | $75 | none (balance debit) | Platform history screenshot saved |
| 2026-12-01 | Exchange B, sale | n/a | Sale | 0.5 ETH sold | $1,800 | 0x7a31bd…09f5c3 | Basis $1,500, gain $300 |
Those hashes are made-up placeholders. Use full hashes in your real file.
Where a platform keeps a balance and never posts an on-chain transaction for an individual bet, there is no hash. In that case the platform’s own account history is your evidence. Export it regularly.
What to save
- Account history exports: CSV or PDF from the platform, downloaded monthly. Accounts get closed and history can vanish.
- Bet slips and confirmations: screenshots with the date visible.
- Wallet and exchange exports: transaction histories from every wallet and exchange you use.
- Price source evidence: the explorer page or exchange record behind each dollar value.
- Any tax forms: W-2G, 1099-DA, or other statements from a payer.
- Your own diary: dated, one line per session or bet, kept in one file.
Keep gambling and crypto records in one place per tax year. If you move coins between your own wallets, log the moves so they are not mistaken for sales.
How long to keep them
The IRS’s general rule is three years from the filing date, longer in some cases. For coins, keep the receipt record until well after you have sold them and the sale year has aged out, since the receipt value is your cost basis. If you’re unsure, keep them longer.
Why the 2026 change makes this more important
From tax year 2026 only 90% of gambling losses can be deducted, and never more than winnings. Every dollar of loss you can prove matters more than before. See Deducting gambling losses, and for how the winnings are valued, Crypto gambling winnings.
Common questions
Is a screenshot of my balance enough?
No. It shows a number at a moment, not wagers, wins and losses. Keep session-level history from the platform plus your own diary.
What if the platform shuts down or locks my account?
Then your own exports are all you have. That is one more reason to download history often. Unlicensed platforms have no regulator to appeal to; see Are offshore sportsbooks legal?.
Do I need to log bets I placed with a stablecoin?
Yes. The dollar value may barely move, but the wager, the result and the date still belong in the diary. Stablecoin records also show your basis if the coin drifts from $1.