Guides
Practical guides to crypto cost basis: what breaks it, what the warnings in your tax tool actually mean, and what the new IRS digital asset reporting forms do about it. Sourced from IRS instructions and vendor documentation, linked so you can check them — here's how we research these. None of it is tax advice.
Missing Purchase History in Koinly: What It Actually Means and How to Fix It
Koinly's missing purchase history warning means a $0 cost basis and inflated gains. Here's what causes it, how to fix it, and when the fix isn't in the app.
Phantom Gains: Why Your Crypto Tax Tool Shows Profits You Never Made
Crypto phantom gains happen when a transfer erases your cost basis and the whole sale gets taxed as profit. The five causes, and how to check your own report.
Crypto's Per-Wallet Cost Basis Switch: What Rev. Proc. 2024-28 Means for Your 2025 Taxes
On Jan 1, 2025 crypto cost basis went universal to per-wallet under Rev. Proc. 2024-28. What the safe harbor snapshot allocates, how to do it, and what breaks.
Form 1099-DA Box 1g: Why Your Crypto Cost Basis Will Be Blank, Wrong, or Read as Zero
Form 1099-DA reports crypto cost basis in Box 1g — but for self-custody, DeFi, and transferred-in coins it's often blank or wrong. How to fix it.
Form 8949 Boxes G–L and Code B: How to Report a Wrong 1099-DA Cost Basis
Form 8949 now has digital asset boxes G, H, I, J, K, and L. Which one your crypto sale goes in, and how code B corrects a 1099-DA cost basis that's wrong.
CoinTracker Cost Basis Wrong or Missing: What Each Flag Means and How to Fix It
CoinTracker's review-suggested flags mean a guessed or $0 cost basis and inflated gains. What each flag assumes, how to fix it, and when the app can't.
We Ran Naive Cost-Basis Rules on a Public Wallet Cluster: $44,975,739 of Phantom Gains
Same engine, same data, one difference: whether self-transfers carry cost basis. On a fully public Ethereum cluster it overstates lifetime gains by $44.9M. Method and balance tie-out included.
Why Your Cost Basis Is Wrong After Moving Crypto Between Your Own Wallets
Moving crypto between wallets you own isn't taxable — but it's where tax software drops your cost basis and invents a gain. Why self-transfers break basis, and how to check yours.
A 5-Event Public Wallet Tied Out: The Ordinary-Scale Case Study
Five on-chain events, cutoff 2021-12-31, ledger 0.097 ETH matched to the chain. The public example at searcher scale — not a whale headline.
27,000 ETH With $0.00 Basis: A Rev. Proc. 2024-28 Allocation, Measured
A public address scanned alone tied out to the wei — and its Rev. Proc. 2024-28 allocation statement still assigned $0.00 basis to all 17 lots. Why a passing tie-out is not basis.
The Only Sale Was Not in the Transaction List: An Arbitrum Scan, Measured
A public address's Arbitrum history: 16 inbound transactions, none outbound. Its one disposal — $366.05 of gain, $0.00 basis — appears only in the internal-transaction index, in an ERC-4337 bundle.
How to Fix Phantom Gains Before You File
A step-by-step remediation guide for crypto phantom gains: confirm the false gain, reunite transfers, reconstruct basis, and correct the return on Form 8949 before you file — not after a notice.
How a $0 Cost Basis Gets Into Your Crypto Tax Report: The Five Mechanisms
A $0 cost basis means your tax software found a sale but no purchase. The five data mechanisms that put the zero in the report — all tool-independent — and how to verify each one in your own records.
Overpaying Crypto Taxes: How Phantom Gains Inflate the Bill You Actually Pay
Phantom gains inflate crypto tax bills three ways: tax on profit that never existed, long-term coins taxed as short-term, and real losses that vanish. How to catch all three before you file.
"Missing Purchase History": A Repair Checklist That Works in Any Crypto Tax Tool
Koinly calls it missing purchase history; other tools flag missing cost basis. Same defect, same fix: a four-pass repair checklist — inventory, import, link, de-duplicate — that works in any tool.
IRS Notice 2026-20: The Crypto Lot-Identification Relief Ends December 31, 2026
IRS Notice 2026-20 lets you identify broker-held crypto lots on your own books through Dec 31, 2026. What the relief covers, why 1099-DA mismatches surface in 2027, and what to do now.