Start Here: Sole Proprietor
You're filing Schedule C on your personal Form 1040, you pay self-employment tax on net profit, and you'll probably owe quarterly estimated tax. Everything below is what we'd hand a new sole prop in their first 30 minutes of research.
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Guidance, not advice. We explain the rules, we don't assess your situation. Always seek financial or tax advice from a qualified CPA, Enrolled Agent, or tax attorney, or contact the IRS. Read our editorial scope →
Your essential reading list
- Schedule C line-by-line — Where every receipt and 1099-NEC ends up on your return.
- Self-employment tax explained — 12.4% Social Security + 2.9% Medicare on net profit, plus the half-SE deduction.
- Quarterly estimated taxes — Safe-harbour rules so you don't get hit with §6654 underpayment penalties.
Calculators you'll actually use
- Self-Employment Tax Calculator — Schedule SE 2026 with the half-SE above-the-line deduction.
- Quarterly Estimated Tax Calculator — 100%/110% prior-year vs 90% current-year safe harbour.
- Home Office Deduction — Simplified $5/sq ft vs the actual-expense Form 8829 method.
- QBI §199A Deduction — 20% pass-through deduction with SSTB phase-out.
- Federal Income Tax Calculator — Combine your wage and SE income at 2026 brackets.
Background guides
- Home office deduction — Exclusive-and-regular-use test under §280A(c).
- QBI §199A deduction — Permanent under OBBBA — when SSTB rules kick in.
- Tax calendar — April 15, June 16, Sept 15, Jan 15 estimated due dates.
- Standard vs itemized — How SE income interacts with above-the-line deductions.
Also useful
- ADHD tax admin — Systems for filers who struggle with paperwork.
- Single-parent self-employment — EITC, dependent care credit, head-of-household.
- Crisis signposting — If you've already missed deadlines or owe back tax.
What to do next
Bookmark the SE tax + quarterly estimated tax calculators. Run them once with current-year numbers. If your net profit is above $80–100k, also read the LLC vs S-Corp guide below.
Different situation? Back to all start-here paths.