5 Mistakes Coinbase Users Make on Their Crypto Taxes

A New Era of Crypto Tax Reporting

The 2025 tax year represents a defining shift in how the IRS monitors cryptocurrency activity. For the first time, custodial exchanges like Coinbase are required to report customer transaction data directly to the IRS using the new Form 1099-DA. Millions of Coinbase users are now receiving these forms, many for the first time, and the learning curve is steep.

While the introduction of Form 1099-DA was intended to bring clarity to digital asset reporting, its first-year implementation has introduced significant confusion. Coinbase itself has acknowledged that the new rules create unnecessary complexity for retail investors, particularly those handling small transaction volumes. For users who have traded, transferred, or held crypto across multiple platforms, the potential for costly filing errors is substantial.

This article examines the five most common tax mistakes Coinbase users make and explains why each one can lead to overpaid taxes, IRS notices, or audit exposure.

Mistake One: Assuming the 1099-DA Tells the Full Story

The most consequential mistake Coinbase users make is treating Form 1099-DA as a complete and accurate summary of their tax obligations. It is not. For the 2025 tax year, Coinbase reports only gross proceeds from crypto sales and exchanges. Cost basis, the original purchase price needed to calculate actual gains or losses, is not reported to the IRS.

This means every transaction on a Coinbase-issued 1099-DA shows only what was received from a sale, not what was originally paid. Without cost basis data, the IRS sees only proceeds. If a user does not independently document and report their acquisition costs, the IRS may treat the entire sale amount as taxable gain.

The scale of this problem is significant. A March 2026 analysis from crypto tax software provider Summ examined 30,000 U.S. users with moderate trading activity and found approximately $435 million in inflated capital gains for the 2025 tax year. The average investor in that sample faced roughly $14,500 in overstated gains, driven almost entirely by incomplete cost basis data on exchange-issued forms.

Coinbase users who file based solely on the information provided by their 1099-DA, without independently verifying and supplementing cost basis records, are virtually guaranteed to overpay.

Mistake Two: Ignoring Activity From Coinbase Pro, Wallet, or Other Platforms

Coinbase users frequently overlook the fact that their 1099-DA covers only transactions conducted on the main Coinbase platform. Activity on the legacy Coinbase Pro platform, Coinbase Wallet, or any external exchange is not included. Users who traded across multiple platforms but file based solely on a single exchange report are submitting incomplete returns.

This gap becomes especially problematic when assets are purchased on one platform and sold on another. If a user bought Bitcoin through a decentralized exchange or self-custodial wallet and later sold it through Coinbase, the selling exchange has no record of the original purchase price. The 1099-DA reports the full sale amount with zero or blank cost basis, making the entire proceeds appear as taxable gain.

The IRS expects taxpayers to aggregate all crypto activity across every platform, wallet, and blockchain into a single, reconciled filing. This requires consolidating transaction histories from every source, not just the exchanges that issue tax forms. Failing to do so creates both underreporting risk, if taxable activity on other platforms goes unreported, and overpayment risk, if cost basis from the original acquisition platform is lost.

Mistake Three: Misunderstanding What Constitutes a Taxable Event

Many Coinbase users believe that only selling crypto for U.S. dollars creates a tax obligation. This is incorrect. The IRS treats a broad range of crypto activities as taxable disposals, including converting one cryptocurrency to another, spending crypto on goods or services, and earning rewards through staking, referral programs, or promotional incentives.

The new reporting rules compound this confusion. Form 1099-DA captures stablecoin transactions, even when no actual gain or loss occurred, because the IRS has not exempted dollar-pegged assets from reporting requirements. Gas fees paid in crypto may also appear as reported transactions. Users who are unfamiliar with the full scope of taxable events frequently underreport their activity or become overwhelmed by the volume of reported transactions and file inaccurately.

A clear understanding of which transactions are taxable disposals, which are non-taxable transfers, and which generate ordinary income is essential for accurate filing. Misclassifying even a small number of transactions can cascade into material reporting errors that attract IRS scrutiny.

Mistake Four: Failing to Reconcile Transfer Activity

Moving crypto between wallets or exchanges that a user personally controls is not a taxable event. The IRS has explicitly confirmed this position. However, exchanges cannot always distinguish between a self-transfer and a sale or payment to a third party. Coinbase may assume that outbound transfers are self-to-self movements, but the receiving platform has no information about the origin or acquisition cost of the incoming asset.

This creates a reconciliation problem. When assets arrive at a new exchange from an external wallet, the receiving platform records a cost basis of zero or leaves it blank entirely. If that asset is later sold, the exchange reports gross proceeds with no cost basis, and the IRS sees what appears to be a 100% capital gain.

Proper reconciliation requires matching every outbound transfer with its corresponding inbound receipt across platforms, verifying that self-transfers are classified as non-taxable, and ensuring that cost basis follows the asset from its original acquisition through every subsequent movement. Without this work, users face inflated gain calculations on every asset that has ever been transferred between platforms.

Mistake Five: Assuming Coinbase Files Your Taxes for You

A surprisingly common misconception among Coinbase users is the belief that because the exchange generates IRS forms, the filing process is handled automatically. It is not. Coinbase reports transaction data to the IRS, but the taxpayer remains solely responsible for calculating gains and losses, reconciling cost basis, completing Form 8949, and filing an accurate return.

This distinction is critical for the 2025 tax year in particular. Because Coinbase is reporting only gross proceeds and not cost basis to the IRS, the burden of proving acquisition costs falls entirely on the taxpayer. Users who assume that their exchange has handled their obligations are the most likely to receive a CP2000 notice, the IRS automated letter that flags discrepancies between what an exchange reported and what the taxpayer filed.

The new Form 8949 now includes dedicated sections for digital asset transactions, using boxes G, H, and I for short-term crypto disposals and J, K, and L for long-term crypto disposals. This separation means the IRS can now isolate crypto activity from traditional equity transactions and match it directly against 1099-DA reports. The system is designed to catch discrepancies automatically.

The Common Thread: Incomplete Data Creates Real Financial Exposure

Each of these five mistakes shares a common root cause: incomplete transaction data. Whether the gap is in cost basis records, platform coverage, transaction classification, or transfer reconciliation, the result is the same. Taxpayers either overpay because the IRS treats unreported cost basis as zero, or they underreport because taxable activity on secondary platforms or wallets was never included.

The introduction of Form 1099-DA has made this problem more visible, not less. For the first time, the IRS has a direct line of sight into exchange-level transaction data, and its automated matching systems will flag returns that do not align with broker reports. Investors who rely on partial data or exchange-generated forms alone are taking on unnecessary risk.

Comprehensive reconciliation, across every exchange, wallet, and blockchain, is the only reliable way to ensure accurate reporting, minimize tax liability, and avoid IRS enforcement actions.

Get Your Crypto Taxes Right the First Time

CryptoConsultz offers a comprehensive Crypto Tax Preparation service designed to solve exactly these problems. Our team reconciles your complete transaction history across every exchange, hardware wallet, and DeFi platform into a single, audit-ready tax package your CPA can file with confidence. Every transaction accounted for. Every cost basis documented. Every taxable event classified correctly.

Schedule a consultation to find out how our tax preparation service can protect you from overpaying taxes, prevent IRS matching errors, and give your CPA the complete, accurate data they need to file your return correctly.