u/chainalytics

Something a lot of crypto traders don't realise until it's too late is that US tax isn't really a once-a-year event. It's pay-as-you-go, and if you bank a big gain mid-year, the IRS expects a slice of it that same quarter, not the following April. Miss that and you can owe a penalty on top, even when you pay every dollar of the actual tax by the deadline.

The rule lives in IRC 6654 and it's an underpayment penalty calculated like interest on what you should have paid each quarter but didn't. Here's the kind of thing that trips people up. You sell into a March rally and realise a $100,000 short-term gain, your tax on that is roughly $24,000 at a 24% bracket. You don't make a Q1 estimated payment because you figure you'll settle up at filing. You do pay the full amount in April. The IRS still charges you a penalty for the months that $24,000 sat unpaid from the Q1 due date, and at recent rates around 8% annualised that's not nothing on a chunk that size.

There are safe harbours that protect you. Generally if you've paid in at least 90% of this year's tax, or 100% of last year's (110% if your prior-year income was over $150k), through withholding or estimates, you dodge the penalty. So one clean move after a big quarter is to either send an estimated payment for that quarter or bump your W-2 withholding if you have a job, since withholding is treated as paid evenly across the year regardless of when it actually happened.

The takeaway is simple. A big realised gain isn't a problem you can fully defer to April, the timing itself carries a cost. If you've had a strong quarter, put the estimate in rather than discovering the penalty when you file.

Some people are going to get a 1099-DA, or see their refund held, for an account they swear they never opened. If that's you, here's how to think about it instead of spiralling.

A 1099-DA under your SSN means some platform told the IRS you had a digital asset transaction. There are really only two explanations. The boring one is an old account you forgot about, some app you signed up for years ago during a hype cycle and never used, often showing an outdated address you don't recognise anymore. The serious one is someone used your SSN to open a crypto account, which is straightforward identity theft.

The way to tell them apart is to stop staring at the form and pull your IRS wage and income transcript at irs.gov. That lists every form filed under your number, so you can see exactly who issued the 1099-DA and what the figure is. If the number is zero or tiny and it's an old platform you half-remember, it's almost certainly just a dormant account and you only need to account for it so your return matches and the hold clears. If you flat out don't recognise the issuer, contact them, tell them it isn't you and ask them to correct it, and file a Form 14039 (Identity Theft Affidavit) with the IRS so they flag your account while it's investigated.

https://preview.redd.it/lo4k6g5bog8h1.png?width=928&format=png&auto=webp&s=ba49407c1327e4c954f1fe0eb4dd60de57080892

The thing to hold onto is that a held refund here usually isn't a bill and isn't an accusation, it's the IRS waiting for your return to line up with a form a third party sent them. You don't owe tax on something you never did. It's a paperwork cleanup, just don't ignore it, because the refund stays paused until the numbers match.

Source: IRS Form 1099-DA reporting; Form 14039 (Identity Theft Affidavit); IRS wage and income transcript.

Been seeing this trip people up so figured I'd write it out. As of 1 Jan 2025 you can't pool all your crypto across every wallet and exchange into one averaged cost basis anymore. That was the "universal" method pretty much everyone used. It's gone, that's Rev. Proc. 2024-28. Now basis is per wallet, per account, each one stands on its own.

The practical version: say you bought 1 BTC at $20k on Coinbase and another at $60k sitting in MetaMask, and you sell the Coinbase one for $90k. Under the old method you might've matched that against the $60k lot and called it a $30k gain. Can't do that now. The Coinbase sale uses Coinbase lots, so you're on the $20k basis and a $70k gain. Same sale, $40k more on paper, purely because of where you sold from.

The IRS did give a one-time safe harbour to allocate your unused basis across wallets as of the start of the year, but that window's basically gone and most people never touched it. If you did nothing your broker probably just defaulted you to FIFO per account.

Honestly it's not the disaster some people make it sound like. Your total basis over your lifetime doesn't change, you're not paying tax on money you didn't make. What it does change is timing, which year the gain lands in, and it punishes you hard if your records are a mess. If you were shuffling coins between wallets in 2024 and never reconciled any of it, deal with that before you file.

Source: IRS Rev. Proc. 2024-28.