No. 01 · RECORDS
Nobody announces this. There is no email that says your records are about to expire. But every major venue serves your own trading history through a window, and the window is smaller than most traders think. Once it closes, the data behind it is gone for good.
I found this out the way most people do: by needing a number I could no longer get. I trained as an accountant before I traded, so my instinct was to go pull the source records. The source records did not exist anymore.
Here is what the venues actually keep, from their own documentation.
Your last 10,000 fills. That is the whole record.
This is not buried in a support thread. It is in the API documentation, stated plainly: responses return at most 2,000 fills, and only the 10,000 most recent fills are available. Ten thousand sounds like a lot. It is not. A systematic trader, or anyone running a bot, can clear it in weeks. Every fill past the ten thousandth is unreachable, permanently, from the venue itself. Third-party indexers only hold what they were already capturing when your trades happened. None of them can go back for you.
Source · Hyperliquid API docs, info endpoint
Three months of income history.
Funding fees, realized P&L, commissions. On Binance futures these flow through the income endpoint, and the documentation says what it keeps: income history only contains data for the last three months. Developers have asked how to reach funding from before the wall since at least 2023. The answer in the official forum is that you cannot. Funding is the single largest recurring cost of holding a perpetual, and the venue that settled it keeps ninety days of it.
Source · Binance developer docs · dev.binance.vision
No more Form 8949, while reporting got stricter.
From tax year 2025 onward, the Coinbase Retail Tax Center no longer provides Form 8949 at all. The help page directs users to subscribe to CoinTracker instead. Read that in context: the same year the IRS began requiring brokers to report your sales on the new Form 1099-DA, Coinbase stopped producing the form you use to reconcile them.
Source · help.coinbase.com, Form 8949
Check your own export before you trust it.
In our own reconciliation work we have found venue exports that collapse same-day perp activity into daily aggregates, which destroys intraday detail you can never get back. Windows and formats change without notice. Pull your export today and look at what is actually in it. Do not assume the interface reflects what the export contains.
Source · First-party reconciliation work
There is no conspiracy here, which is almost worse. Serving you five years of fill-level history costs the exchange money and earns it nothing. Retention is their cost, not their obligation. No regulation requires a crypto venue to keep serving your history to you, and when an exchange shuts down entirely, its records go with it. Anyone who traded on a venue that no longer exists already knows how that ends.
The result is a system where every party keeps exactly the slice that serves them, and nobody is responsible for the total. Your exchange has its corner, for as long as it chooses. Your tax tool has whatever it imported before the windows closed. You are the only party with an interest in the complete record, and you are the one party nobody is keeping it for.
Starting with tax year 2025, US brokers report your crypto sales to the IRS on Form 1099-DA. For that first year the form carries gross proceeds only, not cost basis. Basis reporting from brokers begins with tax year 2026, and even then only for assets you bought on that same platform. If you moved assets between venues, no standard yet carries your cost basis with them. Industry reporting puts full transfer-tracking standards out at 2027 or later.
Put the two facts together. The government's picture of your trading gets sharper every year. Your ability to reconstruct your own side of it gets worse every month, because the underlying records are expiring on the schedule above.
If the numbers ever disagree, the burden of proof is on you. And the evidence you would need is exactly the data being deleted.
A record that has fallen out of an export window cannot be repurchased, subpoenaed, or reconstructed by a smarter tool. It does not exist. The only version of your trading record that survives is the one somebody was writing down as it happened.
Every tax platform, journal, and tracker on the market rebuilds your history from whatever the venues still serve, which means they inherit every gap. The best import pipeline in the world cannot import data that was destroyed before it connected.
None of this requires buying anything. It requires an hour, a calendar reminder, and the willingness to accept that nobody upstream of you is keeping the total. The traders who come through the next few tax years cleanly will be the ones who started writing things down before they needed to.
Start the clock before the window does.