US Capital Gains - Unknown Sale Price and Date

[r01k]

Regarding IRS rules in US, calculating capital gains when the purchase price is not known is based on $0 price. However, what is the technique when the purchase price -more exactly, the cost basis-  is known but the sale price and date are not? Let's say that I got 0.01 BTC for $500 in 2021 and I'm sure that I sold it later during the year, but don't know when or for how much. How do I calculate the gain?

[NotFuzzyWarm]

Use a crystal ball, consult spots on goat innards, write numbers on a wall and blindfolded throw a dart at them or just guess...

[SFR10]

However, what is the technique when the purchase price -more exactly, the cost basis-  is known but the sale price and date are not? Let's say that I got 0.01 BTC for $500 in 2021 and I'm sure that I sold it later during the year, but don't know when or for how much. How do I calculate the gain?

Based on everything you presented, I'm guessing you were keeping it in a wallet that didn't belong to an exchange ^{[regardless of its nature]}... I believe you can still find the missing information ^{[date and its price at the time of sale]} by connecting the dots on an "explorer ^{[look where the output of the first transaction was used as an input]}".

[Poker Player]

Let's say that I got 0.01 BTC for $500 in 2021 and I'm sure that I sold it later during the year, but don't know when or for how much. How do I calculate the gain?

If you don't know how much you sold it for, obviously, you won't be able to calculate it. I understand that you bought it in a CEX and probably sold it in a CEX as well? If so there will be a history at the CEX. Because if it was in a decentralized exchange I don't think you would be eating your head off to declare it, let alone such a small amount. How much would be the profit? $200? $500?

Give us more details, otherwise we will have to consult our crystall ball, as NotFuzzyWarm points out.

[Husires]

Let's say that I got 0.01 BTC for $500 in 2021 and I'm sure that I sold it later during the year, but don't know when or for how much. How do I calculate the gain?

You are more specific about buy date that mean you know the platform or the place you made the purchase from, and thus you can get the Bitcoin address.
All bitcoin data is open source and can be traced by everyone so it will be easy to know the date, signature and selling price.

go to https://blockchair.com/pdf/statement:

• Paste your Bitcoin/Altcoin address
• Select the reporting period
• Download your WALLET STATEMENT

[Myleschetty]

Let's say that I got 0.01 BTC for $500 in 2021 and I'm sure that I sold it later during the year, but don't know when or for how much. How do I calculate the gain?

If you don't know how much you sold it for, obviously, you won't be able to calculate it. I understand that you bought it in a CEX and probably sold it in a CEX as well? If so there will be a history at the CEX. Because if it was in a decentralized exchange I don't think you would be eating your head off to declare it, let alone such a small amount. How much would be the profit? $200? $500?

He can still keep track of his trading history if he some through CEX or DEX.
All he has to do is to check his wallet history for the year the trading was executed if sold through DEX since he knows the quantity of the BTC.

[LeGaulois]

A simple solution is to check your bank statements (assuming you used a bank account to receive the money) since it must be kept X year(s).
If you can access your account online, banks usually have a search function. The good thing is that as it happened in 2021, you wouldn't have to search much.
If you used cash, use any price that suits you lol, since they can't control it.

In the worst case, you estimate a period at which you have sold and compare it with the price by looking at coinmarketcap (I know it's a lazy and a bit risky method but that's what I would do as the last option). Otherwise you really need to find more history, from your wallet, your account on an exchange or whatever.

If you give us more information we can give you more directions to help


the usual pain with the taxes