1099-B
Last updated: 2026-04-27
TL;DR / ELI5
Technical definition: IRS topic: Proceeds from broker transactions. Shows sales proceeds, cost basis when reported to IRS, and adjustments such as wash sales.
What 1099-B is for
1099-B covers Proceeds from broker transactions. Shows sales proceeds, cost basis when reported to IRS, and adjustments such as wash sales.
How it connects to Form 1040
Each box on 1099-B is designed to flow into a specific line or schedule on your federal return (and sometimes state copies). The goal of IRS matching is to ensure the same dollar shows up in the same “bucket” on your return as on the payer’s form.
Common errors to avoid
- Basis ‘missing’ when only proceeds reported
- Wash sale disallowed loss handling
BasilTax extraction
BasilTax can read many 1099-B PDFs, extract the important boxes, and map them into your return so you spend less time retyping and more time verifying.
Common errors
- Basis ‘missing’ when only proceeds reported
- Wash sale disallowed loss handling
Ready to tie every line to your documents?
Upload your W-2s and 1099s—BasilTax extracts fields, computes federal and state, and explains each number with citations.
Frequently asked questions
- What is IRS 1099-B?
- Shows sales proceeds, cost basis when reported to IRS, and adjustments such as wash sales. Topic area: Proceeds from broker transactions.
- Do I need to attach 1099-B to my return?
- You generally do not attach informational forms like 1099s to e-filed returns if the amounts are transcribed correctly—retain PDFs for your records and audits.
- What if my 1099-B is wrong?
- Request a corrected form from the payer and keep documentation. Do not “fix” it silently on the return if the IRS has conflicting third-party data—use the corrected path or explain with a statement when appropriate.
Why verification matters
See how BasilTax traces return lines back to your PDFs so you can file with confidence.