Updated October 18, 2026. Quick answer: Line 17 is for fees charged by accountants and attorneys, line 18 is for office supplies and postage, and line 19 is for retirement plan contributions you made for your employees. If a plan covers you as the owner, your own contribution goes on Schedule 1, not on Schedule C.
Picking the Schedule C business code for your work (2025 chart): Schedule C code for bookkeepers.
Line 17: legal and professional services
The form’s caption reads “Legal and professional services”. The instructions say “Include on this line fees charged by accountants and attorneys that are ordinary and necessary expenses directly related to operating your business.”
“Include fees for tax advice related to your business and for preparation of the tax forms related to your business.” “Also, include expenses incurred in resolving asserted tax deficiencies related to your business.” “For more information, see Pub. 334.”
Line 18: office expense
The caption reads “Office expense (see instructions)”. The instruction is short: “Include on this line your expenses for office supplies and postage.” Supplies used in making a product for sale are handled differently, as covered on the Schedule C lines 20 to 22 page and the Schedule C Part III page.
Line 19: pension and profit-sharing plans
The caption reads “Pension and profit-sharing plans”. The instruction is “Enter your deduction for the contributions you made for the benefit of your employees to a pension, profit-sharing, or annuity plan (including SEP, SIMPLE, and SARSEP plans described in Pub. 560).”
The rule for the owner is separate: “If the plan included you as a” self-employed “person, enter the contributions made as an employer on your behalf on Schedule 1 (Form 1040), line 16, not on Schedule C.” That deduction is explained on the Schedule 1 lines 15 and 16 page.
“This deduction may be subject to limitations. For more information on potential limitations, see Pub. 560.”
Plan filing forms
The instructions also cover reporting: “In most cases, you must file the applicable form listed below if you maintain a pension, profit-sharing, or other funded-deferred compensation plan.” “There is a penalty for failure to timely file these forms.” They name three forms. “File this form if you have a one-participant retirement plan that meets certain requirements.” That is Form 5500-EZ, and the instructions define the term: “A one-participant plan is a plan that covers only you (or you and your spouse).” “File this form electronically with the Department of Labor (at efast.dol.gov) if you have a small plan (fewer than 100 participants in most cases) that meets certain requirements.” That is Form 5500-SF. “File this form electronically with the Department of Labor (at efast.dol.gov) for a plan that does not meet the requirements for filing Form 5500-EZ or Form 5500-SF.” That is Form 5500.
Where the number comes from
Line 17 comes from your invoices and statements from accountants, attorneys and other professionals. Line 18 comes from your receipts for office supplies and postage. Line 19 comes from the plan contributions you made for your employees, as shown in your plan records. For small business plan options, see the Schedule 1 lines 15 and 16 page.
Where it goes next
Each Part II expense line is a step toward the total on line 28. The form describes it as “Total expenses before expenses for business use of home. Add lines 8 through 27b”. Line 29 then reads “Tentative profit or (loss). Subtract line 28 from line 7”. Part II also carries this heading: “Expenses. Enter expenses for business use of your home only on line 30.” Lines 28 and 29 are explained on the Schedule C lines 27a to 29 page and line 30 on the Schedule C line 30 page. The overall form is explained on the Schedule C (Form 1040) page, and the return it attaches to is the Form 1040.
Edition and line numbers
This page reads the 2025 Schedule C (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The schedule’s heading 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 line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Putting the owner’s own plan contribution on line 19. The instructions say to enter it “on Schedule 1 (Form 1040), line 16, not on Schedule C.”
- Treating the deduction as unlimited. The instructions say “This deduction may be subject to limitations.”
- Forgetting the plan filing requirement. The instructions say “There is a penalty for failure to timely file these forms.”
Related: Schedule C (Form 1040), Schedule 1 lines 15 and 16, controlled group solo 401k, 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 18, 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.