Our guide on cost basis methods covers how your gain or loss gets calculated once you have bought the same token more than once. This article looks at a related idea that only matters once you already have some losses sitting in your wallet: tax loss harvesting, and the wash sale question that almost always comes up alongside it.
What tax loss harvesting actually means
Tax loss harvesting is the practice of selling an asset while it is worth less than you paid for it, so that the resulting loss can offset other gains you owe tax on. The mechanics are simple. Say you bought one token at $500 and it is now worth $300. If you sell it, you realize a $200 loss. In many jurisdictions, that realized loss can be used to reduce the taxable gain from a separate, profitable trade you made the same year, which lowers your overall tax bill for that year.
Nothing about this requires you to believe the token is worthless or that you are done with it forever. The strategy is specifically about realizing the loss on paper, not about giving up on the asset. Which is exactly why the next part matters.
Why people ask about buying it right back
If the whole point is to lock in a loss for tax purposes, the obvious next question is: can you just sell the token and immediately buy it back, so your tax position improves while your actual holdings do not change? For publicly traded stocks and securities in the United States, the answer is no. The wash sale rule disallows the loss if you buy a "substantially identical" asset within 30 days before or after the sale. Sell at a loss, buy back the same stock the next day, and the loss is disallowed for that tax year.
The reason this keeps coming up in crypto is that, under current United States tax guidance, digital assets have historically been classified as property rather than as securities, and the wash sale rule as written has applied specifically to securities. That classification is exactly why many crypto investors have discussed harvesting losses and repurchasing the same token shortly after, without the 30-day wash sale restriction that would apply to a stock. This is a real and frequently cited difference, not folklore. It is also an area regulators and lawmakers have proposed changing more than once, and proposals to extend wash sale treatment to digital assets have come up in budget and tax legislation discussions. Whether a wash-sale-style rule applies to crypto in any given tax year, in any given country, is a question of current law in that jurisdiction at that moment, not a fixed fact about how crypto works.
This varies enormously by country
The United States treatment described above is not a global standard. Other countries have their own rules about realized losses, holding periods, and anti-abuse provisions, and some already apply wash-sale-style restrictions to crypto specifically or interpret existing rules to cover it. Some jurisdictions do not permit capital losses to offset certain types of gains at all, or only allow it within strict limits. None of this is safe to assume based on what you have read about another country's rules, including the United States example above.
What this has to do with your wallet activity
A self-custody wallet like a Base wallet does not know or care about any of this. It will execute a sell and a subsequent buy of the same token with no restriction either way, because the wash sale question is a tax law concept, not a blockchain concept. The only place this matters is when you or your tax software later classify your transaction history for a filing. That makes two things worth doing if you are thinking about harvesting a loss.
First, keep records of exactly when each sale and each repurchase happened, down to the date and the amount, the same habit covered in our record-keeping guide. If a 30-day or similar window matters in your jurisdiction, you need the actual timestamps to know whether you are inside or outside it.
Second, understand that harvesting a loss only changes when a loss is realized. It does not change the price of the token, the merits of the project, or whether you should hold it going forward. Selling into a loss purely to trigger a tax event, without regard for what you actually think the token is worth, is a decision with trade-offs on both sides: a smaller tax bill this year against being out of the position, even briefly, while prices move.
This is not tax advice
Whether tax loss harvesting applies to you, whether a wash-sale-style restriction applies to your trades, and how any of this should be reported, depends entirely on your jurisdiction and on rules that change over time through legislation and guidance. This article explains the general shape of the strategy and the reason crypto's treatment has differed from stocks in some places. It is not a recommendation to harvest losses, repurchase tokens, or structure your trading around tax outcomes. Talk to a qualified tax professional in your own jurisdiction before making decisions based on any of this, and bring your transaction records with you.