Why it matters
The form is where the detail behind the capital gain or loss lives. A missing basis, a wash sale or a transaction the broker did not report can change the tax, so the client needs the trade records.
Example
A client sells stocks and cryptocurrency during the year. The preparer lists each sale on Form 8949, separates the short-term and long-term transactions and carries the totals to Schedule D.
Related terms
Questions about Form 8949
Does every sale go on Form 8949?
Most sales of capital assets are reported there, but some transactions are reported directly on Schedule D or on another form. The instructions explain the exceptions.
What if the broker did not report the basis?
The client needs the purchase records or the broker's supplemental statement. Without the basis, the preparer may have to treat it as zero, which overstates the gain.