1099 Estimated Tax Planner | Stillion CPA

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Calculators

Free tools built by the CPA who prepares the returns. Each one lists the rules and figures it uses.

All 12 calculators

S-Corp vs. Sole Proprietor 1099 Estimated Tax Planner Solo 401(k) and SEP-IRA QBI Deduction Estimator (§199A) Entity Comparison True Runway

Most used

S-Corp vs. Sole Proprietor ›1099 Estimated Tax Planner ›Withholding Checkup ›

When a tool isn’t enoughEvery calculator links to the service or model that covers the rest of the question.Send an inquiry

Services

Tax, books, elections and reporting for owner-run businesses and investors. I do the work myself, under an engagement letter that sets scope and fee first.

Form 1040 and California Form 540 Form 1120-S and California Form 100S Estimated payments Extensions Owner compensation The §199A deduction Shareholder basis Depreciation choices Go to the Tax page

Start with a calculator

Withholding Checkup ›S-Corp vs. Sole Proprietor ›Rental Property Analyzer ›

Excel modelsThe reporting package, C-to-S conversion and QSBS workbooks are built the way I build them for clients.See the models

Models

Excel workbooks for reporting and tax analysis. Licensed per user or firm; you own your copy.

Financial Reporting Package v2.1 Consolidation Edition v1.0 C-Corp to S-Corp Conversion Analyzer v2.0 QSBS §1202 Analyzer v1.0

What’s inside

21 tabs, 28,550 formulas (FRP) ›§1374 and LIFO recapture (C→S) ›Pre- and post-2025 §1202 rules ›

Rather have me run it?I can build the reporting package or run the analysis as an engagement.Send an inquiry

1099 Estimated Tax — Pro Planner

A complete quarterly plan for self-employment income: choose your safe harbor, handle uneven income, see the full breakdown, then print or export it.

Filing status

Expected 1099 income

Business expenses

Other household income

Federal tax withheld

Children under 17

Safe harbor target

California resident

Income is uneven across the year

Q1 % of income

Q2 %

Q3 %

Q4 %

Tax breakdown

Quarterly schedule — 2026 tax year

Quarter	Due date	Federal	California

More for business owners

BUS-01S-Corp vs. Sole ProprietorEstimates self-employment tax savings from an S election, after a reasonable salary and the cost of running payroll.Business owners BUS-03Solo 401(k) and SEP-IRAMaximum contribution under each plan by entity type and age, and which plan allows more.Business owners BUS-04QBI Deduction Estimator (§199A)The 20% qualified business income deduction, with the income thresholds and the specified service trade or business rules.Business owners BUS-05Entity ComparisonSole proprietorship, S-corporation and C-corporation compared on the same profit, with optional California entity taxes.Business owners