Updated October 23, 2026. Quick answer: The 2025 IRS chart lists 999000 for unclassified establishments (unable to classify); it has no 999999 row. The code goes on line B of Schedule C. The chart’s two-step rule says to find the activity first, so a neighboring row may read closer, depending on the principal source of your receipts.
What the 2025 chart lists for unclassified work
The 2025 chart ends with one row that does not describe an activity at all. It is a single row and its code is 999000; the chart has no 999999 row, and a search of the instructions finds no other code for unclassified work.
| Code | Wording on the IRS chart |
|---|---|
| 999000 | Unclassified establishments (unable to classify) |
How line A and line B treat it
Line A asks for a description of the work: “Describe the business or professional activity that provided your principal source of income reported on line 1.” Line B asks for the code: “Enter on line B the six-digit code from the Principal Business or Professional Activity Codes chart” The code goes in the box on line B, beside the description.
The row names no profession or product. Line A still asks for a description of the activity. A description written for this situation would be an example of the kind of description, not IRS wording: custom work for a small number of local customers.
Catch-all rows inside an activity family
The chart’s catch-all wording appears in a few other rows too, each tied to an activity family. They show how the chart words a leftover category inside an activity.
| Code | Wording on the IRS chart |
|---|---|
| 238990 | All other specialty trade contractors |
| 621399 | Offices of all other miscellaneous health practitioners |
| 561790 | Other services to buildings & dwellings |
| 237990 | Other heavy & civil engineering construction |
Compare “All other specialty trade contractors” and “Offices of all other miscellaneous health practitioners” with “Unclassified establishments (unable to classify)”. The first two are leftover rows worded inside a family of work, while the last one carries no activity wording at all.
The chart’s rule has two steps: “Select the category that best describes your primary business activity”, and then “Then select the activity that best identifies the principal source of your sales or receipts”.
The process, and what the instructions leave unsaid
The order of the chart’s steps matters here. The rule asks you to “Select the category that best describes your primary business activity”, then “Then select the activity that best identifies the principal source of your sales or receipts”, and only then to “Now find the six-digit code assigned to this activity”. The row for unclassified establishments is reached at the end of that search, not at the start of it.
The instructions give no rule for when the row on the chart named unclassified establishments is the one to enter. A search of the Schedule C instructions and the form finds that row only in the chart, with no sentence explaining it, so this page does not say when it applies. What the chart says is the row’s wording and nothing else.
Where the code goes next
Whichever code ends up on line B, it sits beside the line A description on Schedule C (Form 1040). The income side of the schedule is covered on Schedule C line 1, and the return the schedule attaches to is on Form 1040.
Edition and chart year
This page reads the 2025 Schedule C (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-23 (byte-identical to the archived copies). They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, 1040-SS, 1040-NR, or 1041”. Check the tax year printed on the schedule you are filling in and use the chart that comes with that year’s instructions, because a different year’s chart can list different codes or reword them.
Common mistakes
- Looking for a code 999999. The 2025 chart lists “Unclassified establishments (unable to classify)” under code 999000 and no other.
- Starting at the last row. The chart’s first step is to “Select the category that best describes your primary business activity”, so the search is for the activity before any code.
- Skipping line A. The instructions say “Describe the business or professional activity that provided your principal source of income reported on line 1.”
Related: Schedule C (Form 1040), Schedule C line 1, and Form 1040.
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Answer againSources
- Instructions for Schedule C (Form 1040), Profit or Loss From Business (2025): https://www.irs.gov/pub/irs-pdf/i1040sc.pdf
- Schedule C (Form 1040), Profit or Loss From Business (2025): https://www.irs.gov/pub/irs-pdf/f1040sc.pdf
Read from the IRS documents linked above on October 23, 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.