Updated October 17, 2026. Quick answer: Code M goes in column (f) of Form 8949 when you report multiple transactions on a single row under Exception 2 (an attached statement) or the special provision for certain corporations, partnerships and securities dealers. Enter -0- in column (g) unless another code requires an adjustment. The special provision is narrow, and individuals are not eligible except in rare circumstances.
What code M means
The default rule is one transaction per row. The instructions say “Enter the details of each transaction on a separate row”, then “There are exceptions to the rule that you must report each of your transactions on a separate row of Part I or II.” Code M is the code that goes with those exceptions. The column (f) table row reads “You report multiple transactions on a single row, as described in Exception 2 or Special provision for certain corporations, partnerships, securities dealers, and other qualified entities under Exceptions to reporting each transaction on a separate row, earlier”.
Exception 2: an attached statement
The instructions describe it this way: “Instead of reporting each of your transactions on a separate row of Part I or II, you can report them on an attached statement containing all the same information as Parts I and II and in a similar format” (the parenthetical lists “description of property, dates of acquisition and disposition, proceeds, basis, adjustment and code(s), and gain (or loss)”). “Use as many attached statements as you need.” “Enter the combined totals from all your attached statements on Parts I and II with the appropriate box checked.”
Their example: “For example, report on Part I with box B or box H checked all short-term gains and losses from transactions your broker reported to you on a statement showing basis wasn’t reported to the IRS.” “Enter the name of the broker followed by the words “see attached statement” in column (a).” “Leave columns (b) and (c) blank.” “Enter “M” in column (f).” “If other codes also apply, enter all of them in column (f).” “Enter the totals that apply in columns (d), (e), (g), and (h).” “If you have statements from more than one broker, report the totals from each broker on a separate row.”
Summary totals alone do not satisfy the rule: “Don’t enter “Available upon request” and summary totals in lieu of reporting the details of each transaction on Part I or II or attached statements.”
The special provision for certain entities
A second route exists, but it is narrow. The instructions say “This special provision applies to certain corporations, partnerships, securities dealers, and nonprofit organizations.” “Individual taxpayers aren’t eligible except in rare circumstances.”
It applies if “You file Form 1120-S or Form 1065, or are a taxpayer exempt from receiving Form 1099-B or Form 1099-DA”, and the second requirement is “You must report more than five transactions for that part.”
The filing steps are: “If this provision applies to you, enter the summary totals on line 1.” “Enter “Available upon request” in column (a).” “Enter “M” in column (f).” “Don’t use a separate row for the totals from each broker.”
What to enter in column (g)
The table’s rule for code M is “Enter -0- in column (g) unless an adjustment is required because of another code.” For another code on the same row, see its own page. For example, wash sale losses are covered on Form 8949 code W.
If a row needs two codes, the instructions say “If more than one code applies, enter all the codes that apply in alphabetical order (for example, “BOQ”).” “Don’t separate the codes by a space or comma.” For the net adjustment they say “If you entered more than one code in column (f) on the same row, enter the net adjustment in column (g).”
Two cautions
The first is about electing to defer gain: “Exception 2 is not available for the election to defer eligible gain by investing in a QOF.” The second is about e-filing: “If you efile your return but choose not to report each transaction on a separate row on the electronic return, you must attach Form 8949 to Form 8453 (or the appropriate form in the Form 8453 series) and mail the forms to the IRS.” Broker-form boxes are explained on the Form 1099-B box 5 and box 12 page.
Where it goes next
Column (h) is the result. The instructions say “First, subtract the cost or other basis in column (e) from the proceeds (sales price) in column (d).” “Then take into account any adjustments in column (g).” “Enter the gain (or loss) in column (h).”
Form 8949 feeds the Schedule D. The instructions open with “Complete Form 8949 before you complete lines 1b, 2, 3, 8b, 9, or 10 of Schedule D.” They also say “Include on your Schedule D the totals from all your Parts I and II.” The totals line at the bottom of Part I tells you to “Enter each total here and include on your Schedule D, line 1b (if Box A or Box G above is checked), line 2 (if Box B or Box H above is checked), or line 3 (if Box C or Box I above is checked)”. Part II says to “include on your Schedule D, line 8b (if Box D or Box J above is checked), line 9 (if Box E or Box K above is checked), or line 10 (if Box F or Box L above is checked)”. The Schedule D itself is explained on the Schedule D page, and the full set of form instructions is on Form 8949 instructions.
Edition and line numbers
This page reads the 2025 Form 8949 and its 2025 instructions, along with the 2025 Schedule D instructions where cited, the current files irs.gov served on 2026-10-17. They are the forms for the tax year 2025 return, filed in 2026. Check the tax year printed on the form you are filling in and use the column letters and codes on that year’s form, because a different year’s form can letter its columns or word its codes differently.
Common mistakes
- Treating M as a shortcut for any long list of sales. The special provision says “Individual taxpayers aren’t eligible except in rare circumstances.”
- Writing “Available upon request” in an Exception 2 row. The instructions say “Don’t enter “Available upon request” and summary totals in lieu of reporting the details of each transaction on Part I or II or attached statements.”
- Leaving off the other codes. The instructions say “If other codes also apply, enter all of them in column (f).”
Related: Form 8949 instructions, Schedule D, Form 1099-B box 5 and box 12, and Form 1099-B boxes explained.
Sources
- Instructions for Form 8949 (2025): https://www.irs.gov/pub/irs-pdf/i8949.pdf
- Form 8949 (2025): https://www.irs.gov/pub/irs-pdf/f8949.pdf
Read from the IRS documents linked above on October 17, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.