1099-B to Form 8949: Which Box, and When to Skip It

Form 8949 sorts sales two ways. short-term sales go in the first part of the form and long-term sales in Part II, and within each part you check one box that says how the basis was reported, according to the IRS Instructions for Form 8949 and Schedule D. Box A is short term with the basis reported to the IRS, which on your 1099-B means box 12 is checked. Box B is short term with basis not reported. Box C is short term with no 1099-B at all. Boxes D, E and F are the long-term versions of the same three.

There is also a shortcut. Covered sales with no adjustments may not need Form 8949 at all.

If you have not yet worked through the 1099-B itself, start with how to read Form 1099-B. Everything below assumes you know where box 2 and box 12 sit.

Matching each 1099-B line to a box

Read two things off each sale. Box 2 gives the term. Box 12 tells you whether the basis went to the IRS.

1099-B shows	Form 8949 box
Short term, box 12 checked	A
Short term, box 12 not checked	B
Short term, no 1099-B received	C
Long term, box 12 checked	D
Long term, box 12 not checked	E
Long term, no 1099-B received	F

Your own dates still matter. If box 2 has the term wrong because a transferred lot came in with a bad acquisition date, the holding period you can prove from your purchase records decides which part the sale belongs in.

When you can skip Form 8949

The exception is narrow and useful. A sale qualifies when box 12 shows the basis was reported, there are no adjustments, so no wash sale and no code of any kind, and nothing else requires Form 8949. Those sales can go on Schedule D as totals: line 1a for short term, line 8a for long term.

The test applies sale by sale. A covered short-term sale with a figure in box 1g fails it even though box 12 is checked, because the wash sale adjustment needs code W in column (f) and an amount in column (g), and those columns exist only on Form 8949. Check every line.

A return can use both routes in the same year. The clean covered sales go to Schedule D in one line of totals, and anything with a code, a missing basis or no 1099-B goes on Form 8949.

What goes in each column

The columns run (a) through (h). Column (a) describes the property, (b) is the date acquired, (c) the date sold, (d) the proceeds and (e) the basis. Column (f) holds the code, (g) the adjustment, and (h) the gain or loss.

The common codes for stock sales:

• W, for a wash sale loss disallowed.
• B, when the basis on the 1099-B is wrong.
• E, for selling expenses the 1099-B did not reflect.

With code B, put the correct basis in column (e), the figure your confirmations support. A wash sale amount shows up in 1099-B box 1g, and reading that box properly is its own job, covered in 1099-B box 1g and the wash sale loss disallowed.

Column (h) is arithmetic. Take proceeds, subtract basis, and apply the adjustment in (g). A code W amount is added back, so it shrinks the loss.

Three lines from one consolidated 1099

All three sales below are hypothetical, as are the companies.

The first is 50 shares of ABC, held a few months, box 12 checked, no 1g. The second is 100 shares of XYZ, also short term with box 12 checked, carrying a 1g figure of 240.00 because you bought 40 shares back within the window. The third is 20 shares of DEF, held for years and bought before the covered dates, so box 5 is checked, box 12 is blank and so is the basis in 1e.

Notice what moved XYZ onto the form. Its box was A, same as ABC. The code made the difference. Without the wash sale it would have joined ABC on line 1a.

DEF depends entirely on your records. The cost basis you enter in column (e) has to be one you can back up with the original confirmation or an old statement, since the IRS never received a figure from the broker. Keep that paper with your tax records. If a 1099-B line does show a basis and that basis is wrong, the correct figure goes in (e) with code B.

Checking what the software did

Tax software usually imports a consolidated 1099 in one step, and the import is where problems hide, because a missed line or a dropped code looks perfectly tidy on screen. Before you file, compare the software’s totals for proceeds, basis and adjustments against the summary page of your 1099-B, box by box: short term reported, short term not reported, long term reported, long term not reported.

They should match to the cent. When they do not, look first for a noncovered sale with no basis entered, a wash sale that lost its code W, or a sale the import put in the wrong part.

The IRS instructions for both forms are the authority on every box and code, including the rarer ones not covered here. For anything they leave unclear in your own case, such as a basis you cannot fully document from old statements, ask a tax professional.