Mistake 1 — Not Reporting Small Transactions
One of the most widespread misconceptions in crypto taxes is that small transactions don't need to be reported. This is wrong. The IRS has no de minimis exemption for cryptocurrency. Every taxable event — even a $12 swap, a $3 staking reward, or a minor NFT sale — must be reported. The rules that apply to a $500,000 Bitcoin sale apply equally to a $50 altcoin trade. Ignoring small transactions might seem harmless, but it adds up across a year of active trading and creates a pattern of underreporting that can become significant.
The IRS is aware that many traders under-report small transactions precisely because they assume the amounts are too small to matter. As enforcement technology improves — particularly blockchain analytics tools that can trace wallet activity — small unreported transactions are increasingly findable. The safest approach is to track everything from the start, which is also the easiest approach if you're using crypto tax software rather than manual spreadsheets.
Mistake 2 — Using the Wrong Cost Basis Method
The IRS allows several cost basis accounting methods for crypto: FIFO (First In, First Out), HIFO (Highest In, First Out), LIFO (Last In, First Out), and Specific Identification. The method you choose has a major impact on how much tax you owe in any given year. FIFO is the default in most tax software, but it is not always the most tax-efficient. FIFO sells your oldest (and often lowest-cost-basis) coins first, which can maximize your taxable gains if crypto prices have risen over time.
HIFO — which sells your highest-cost-basis coins first — is typically the most tax-efficient method because it minimizes the gain on each disposal. For long-time holders who bought at various price points, switching from FIFO to HIFO can meaningfully reduce the tax bill. However, you must consistently apply your chosen method and maintain records that support it. Switching methods between years can be done but requires careful documentation. Many traders leave significant money on the table simply by using the default FIFO method without considering alternatives.
Mistake 3 — Not Tracking Staking and Yield Rewards as Income
Staking rewards, yield farming income, and lending interest are taxable as ordinary income when received — not when you eventually sell the tokens. The IRS confirmed this in Revenue Ruling 2023-14. This means if you earned 0.5 ETH in staking rewards throughout the year and ETH was worth $2,000 when each reward was received, you have ordinary income to report equal to the USD value at each receipt — regardless of whether you still hold those tokens or whether ETH's price subsequently dropped.
This creates a painful scenario: you receive staking rewards worth $10,000 during the year (taxable income), then the market crashes and those tokens are now worth $2,000 when you file your taxes. You still owe income tax on the $10,000 you received, even though your holdings are now worth much less. Tracking reward income throughout the year — not just at tax time — is essential for accurate reporting and for managing your tax liability through strategies like harvesting losses or adjusting reward claim frequency.
Mistake 4 — Forgetting That DeFi Activity Is Taxable
Many DeFi users treat on-chain activity as outside the tax system because there are no 1099 forms and no centralized intermediary watching. This is a dangerous misunderstanding. Every token swap on Uniswap, every liquidity pool deposit and withdrawal, every yield claim — these are all taxable events under IRS property rules. The absence of a tax form does not mean the activity is not taxable; it just means you are responsible for tracking it yourself.
Traders who did hundreds of swaps, provided liquidity on multiple protocols, and farmed yield across several chains in a single year may have thousands of taxable events they've never reported. The IRS has increasingly sophisticated tools for identifying on-chain activity, and receiving a letter about unreported DeFi income years after the fact — when records are hard to reconstruct — is a situation you want to avoid entirely. Starting to track DeFi activity now, even retroactively, is far better than never tracking it.
If your tax software can't see your original purchase — because a wallet or exchange is missing — it may assume a $0 cost basis on your sales. A $5,000 sale of coins you bought for $4,800 looks like a $5,000 gain instead of a $200 gain. Fix completeness before you file.
Mistake 5 — Missing Deductible Losses and Tax Loss Harvesting
Most traders focus on avoiding taxes on gains and forget that losses are a tax asset. If you have crypto positions sitting at a loss, selling them before year-end locks in a capital loss that can offset your capital gains dollar-for-dollar. If your losses exceed your gains, up to $3,000 of the excess loss can offset ordinary income each year, with the remainder carrying forward to future years. This strategy — called tax loss harvesting — can meaningfully reduce your tax bill if timed correctly.
Unlike stocks (which have wash sale rules preventing you from repurchasing the same security within 30 days of selling at a loss), cryptocurrency is currently not subject to wash sale rules under US law. This means you can sell a crypto asset at a loss to harvest the deduction, then immediately buy it back. This may change in the future — legislation has been proposed to extend wash sale rules to crypto — but for now the window remains open. A crypto tax professional can help you identify harvesting opportunities before the end of the tax year.
Mistake 6 — Not Keeping Records Long Enough
Many traders delete old exchange accounts, lose access to wallets, or simply stop tracking historical records once they've filed. This creates problems when they need to reconstruct cost basis years later — for example, when they finally sell coins bought in 2018. The IRS standard audit window is 3 years from the filing date for most returns, but it extends to 6 years if you omit more than 25% of gross income. There is no statute of limitations at all for fraudulent returns.
Beyond audit risk, you need historical cost basis records for any asset you're still holding. If you bought ETH in 2020 and haven't sold it yet, you need those 2020 purchase records to calculate your gain when you eventually do sell — potentially years from now. Crypto tax software that stores your full transaction history in the cloud is one of the best investments you can make for long-term record-keeping. Keeping exported CSV files and PDF reports from each tax year in a secure location provides an additional backup.