Tax · Internal Revenue Service

Fill IRS Schedule C programmatically from bookkeeping data.

Pull income and expense totals straight from your accounting system and let SimplyFill render the official Schedule C — Part I income, Part II expenses, and the net profit line — as a flattened, file-ready PDF.

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What is Schedule C (Form 1040)?

Schedule C, Profit or Loss from Business, reports the income and deductible expenses of a sole proprietorship or single-member LLC. It attaches to Form 1040 and feeds net profit into self-employment tax.

Who files it?

Sole proprietors, freelancers, gig workers, and single-member LLCs file a Schedule C with their 1040 each year. Bookkeeping and tax apps need to render it from category totals.

Why filling Schedule C (Form 1040) by hand hurts

Schedule C has 20+ numbered expense lines (advertising, car, depreciation, wages…) plus the Part III cost-of-goods-and-services section — all behind IRS AcroForm names like `topmostSubform[0].Page1[0].f1_18[0]`. Mapping each expense category to the right `f1_NN` is tedious and quietly breaks when the form is revised.

Fill Schedule C (Form 1040) in one call

Render a Schedule C from expense-category totals

fill-schedule-c.ts

Node.js

const res = await fetch('https://api.simplyfill.app/v1/generate', {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${process.env.SIMPLYFILL_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    template: 'schedule_c_2025',
    data: {
      proprietor_name: 'Ada Lovelace',
      business_name: 'Lovelace Analytics',
      business_code: '541511',
      gross_receipts: 210000,
      advertising: 4200,
      net_profit: 168500,
    },
  }),
})

const { url } = await res.json()

Fields on Schedule C (Form 1040)

Real form fields are named for the PDF spec, not for humans — so a single value can hide behind something like topmostSubform[0].Page1[0].f1_02[0]. SimplyFill lets you map your own readable keys to these once, then forget they exist.

Raw PDF field name	What it means
topmostSubform[0].Page1[0].f1_01[0]	Name of proprietor
topmostSubform[0].Page1[0].f1_03[0]	Principal business or profession
topmostSubform[0].Page1[0].f1_07[0]	Business code (Part I)
topmostSubform[0].Page1[0].f1_18[0]	Line 1 — gross receipts or sales
topmostSubform[0].Page1[0].f1_30[0]	Line 8 — advertising expense
topmostSubform[0].Page1[0].f1_60[0]	Line 31 — net profit or loss

Frequently asked questions

Can I generate Schedule C together with the 1040?

Yes. Use the bulk endpoint with both templates and one data payload; SimplyFill returns the 1040 and Schedule C as a single combined envelope ready for review or e-file packaging.

Do I map every expense line by hand?

You map each readable category (e.g. `advertising`, `car_and_truck`) to its line once in a mapping. After that, sending your category totals fills the right `f1_NN` fields automatically.

Does SimplyFill compute net profit?

No. SimplyFill places the values you provide — your accounting system or tax engine computes line 31. We render exactly what you send onto the official form.

Is Part III (cost of goods sold) supported?

Yes — all parts of Schedule C are available as fields, including Part III COGS and Part IV vehicle information. Send only the fields relevant to the filer.