How a River export becomes a Form 8949 worksheet line, and which rows never become one.

Not tax advice · last updated 25 October 2026

River CSV to Form 8949

River can hand you more than one CSV. BasisFix reads two current shapes plus the older sample format. The result is a review with a tax pro, not a return. Confirm the columns against the file you actually downloaded. A header BasisFix does not recognize is reported and skipped.

Account Activity

The Account Activity file uses Date UTC, Reference Code, Transaction Type, Sent Amount/Currency, Received Amount/Currency, and Fee Amount/Currency. Split columns (Sent Amount and Sent Currency) are accepted too. An optional Fair Market Value USD column supplies income and declared receive basis.

• Buy. Crypto received, USD sent. Basis is the USD sent plus a USD fee. A fee charged in bitcoin reduces the coins acquired.
• Sell. Crypto sent, USD received. Proceeds are the USD received minus a USD fee. A bitcoin fee increases the quantity sold. This is the row that can become a Form 8949 line.
• Send and Auto Withdrawal. A transfer out of the River account. It is not a sale. If another imported file receives the same coins, basis and the original date move. If nothing matches, the lots stay at River and a warning is raised.
• Receive. A transfer in. Fair market value, when the column has it, is declared basis only if the receive is not matched to a send.
• Interest Payout, Mining Payout, Referral Reward. Ordinary income at fair market value. Each payout starts a new lot. They are listed on the income summary, not on Form 8949.
• Cash Deposit and Cash Withdrawal. Fiat moving in or out. No lot, no sale.
• Internal Transfer of the same asset. The coins never left the River account. No second lot and no sale. A transfer between two different cryptocurrencies is skipped for you to split by hand.

Bitcoin Activity

The Bitcoin Activity file uses a date, a sent or received amount with its currency, a fee, and a tag: Buy, Sell, Mining, Withdrawal, Income, or Interest. A bare fee number is read in the row’s currency. The USD Value column is already the economic amount, so the fee is not added to it a second time. A bitcoin fee reduces a buy and increases a sell.

• Buy opens a lot at the USD value.
• Sell is the Form 8949 candidate.
• Interest and Mining are ordinary income and open lots. A tag of Income is ordinary income in the “other” category.
• Withdrawal is a transfer out, not a sale, until a matching receive shows up in another file.

A fictional 2024 slice

The sample Account Activity file in this repository is invented. Under FIFO, the 2024 sale of 0.02 BTC has proceeds of 1,190.00, basis of 500.00 from the 2023 lot, and a short-term gain of 690.00. HIFO uses the higher-basis 2024 lot instead, and the gain is 388.00. Interest income on that sample is 40.00, mining is 80.00, and the referral reward is 20.00. A second interest row with no fair market value is flagged and left out of the income total. None of those income rows appear on the Form 8949 worksheet.

The sample Bitcoin Activity sale is 0.004 BTC in 2024. FIFO gain on that fictional row is 90.00 short-term, with interest 8.50, mining 12.00, and other income 4.00.

Both sample files use the River account. They are separate examples, not two exports of one customer. Load one at a time. Importing both pools every lot in that account, so a sale in one file can consume a purchase from the other.

From the file to the preview

1. Download the CSV from River yourself. BasisFix never signs in to River.
2. Open the reconciler and drop the file in. The parse runs in the browser.
3. Pick the tax year and FIFO, HIFO, or specific identification. Build the free preview and read the warnings.
4. The export of the worksheet 8949 CSV and the Schedule D summary stays locked until the license-key check on this machine accepts a key. The dev key in this build does not contact a payment service.

Coinbase, Kraken, Cash App, and a generic column map still import beside a River file, which is how a withdrawal and a later wallet sale stay one lot. Read How to file Form 8949 for Bitcoin for the box letters, the holding period, and what the worksheet leaves out. River’s own Cost Basis column is a different number from the one BasisFix computes; see River’s Cost Basis column. The demo report shows a different fictional year, built from the classic sample set.

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