Updated October 30, 2026. Quick answer: The 2025 chart lists 541310 for architectural services and 541330 for engineering services, with 541340 for drafting, 541350 for building inspection and 541320 for landscape architecture. The code goes on line B. The row that reads closest depends on the principal source of your receipts.
Design and engineering rows on the chart
Five neighboring rows cover this kind of work. Two are named for the professions themselves.
| Code | Wording on the IRS chart |
|---|---|
| 541310 | Architectural services |
| 541330 | Engineering services |
| 541340 | Drafting services |
| 541350 | Building inspection services |
| 541320 | Landscape architecture services |
The first two read “Architectural services” and “Engineering services”. The remaining three describe related services by task: “Drafting services”, “Building inspection services” and “Landscape architecture services”.
Describing the work on line A
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.
An example of the kind of description, not IRS wording: a line A phrase that states the type of projects you take on, such as home plans or structural calculations, and the clients who hire you. The specific discipline can be named there even where the code is broader.
Choosing between neighboring rows
Someone who draws plans but does not design them would compare with “Drafting services”, while someone who mainly reviews finished buildings would compare with “Building inspection services”. A sole practitioner who does both designing and drafting has two activities to weigh, so the question becomes which one brings in more of the receipts.
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”.
Sibling rows in the same section name other technical work.
| Code | Wording on the IRS chart |
|---|---|
| 541360 | Geophysical surveying & mapping services |
| 541370 | Surveying & mapping (except geophysical) services |
| 541380 | Testing laboratories & services |
| 541600 | Management, scientific, & technical consulting services |
Words the chart uses and words it leaves out
The chart names architectural services, engineering services, drafting and building inspection in plain terms. A search of the chart wording finds no row that names surveyors by title, though “Surveying & mapping (except geophysical) services” describes the activity. It also has no engineering services row split by discipline, and the only other engineering wording is in a construction row, “Other heavy & civil engineering construction”.
If you run a second, separate business, the instructions say: “If you owned more than one business, complete a separate Schedule C for each business.”
Where to go next
The code sits on line B beside the line A description on Schedule C (Form 1040). Fees from clients start at Schedule C line 1, gross receipts or sales. Equipment bought for the practice appears in Form 4562, and an office at home is covered at the home office deduction page. Landscape work has its own listing at Schedule C code for landscapers, and the full list of Schedule C business codes lists every row.
Edition and chart year
This page reads the 2025 Schedule C (Form 1040) and its 2025 instructions, 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
- Treating architectural and engineering work as one row. The chart lists “Architectural services” and “Engineering services” separately.
- Overlooking the drafting and inspection rows. Their wording is “Drafting services” and “Building inspection services”.
- Picking by title rather than by receipts. The chart says “Then select the activity that best identifies the principal source of your sales or receipts”.
Related: Schedule C (Form 1040), Schedule C business codes: the full IRS list, Schedule C line 1, gross receipts or sales, the home office deduction page, and Schedule C code for landscapers.
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- Instructions for Schedule C (Form 1040), Profit or Loss From Business (2025): IRS archived PDF (irs.gov)
- Schedule C (Form 1040), Profit or Loss From Business (2025): IRS archived PDF (irs.gov)
Read from the IRS documents linked above on October 30, 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.