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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

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

Models

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

All models

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
James Stillion, CPA · CA license 157015

Decisions needgood numbers.

I work alongside owners and founders on the numbers behind their decisions: tax planning, monthly accounting, S-corporation elections, and the reporting and models behind a hire, a purchase, a financing or a change of entity. Start with one of 12 free calculators or 4 Excel models, or send an inquiry.

Browse all 12 calculators What I do

Should you elect S-corp status?

LIVE · 2026
SE tax as a sole proprietor$21,194
Payroll tax on the salary$13,005
Payroll and admin cost−$2,400
Estimated yearly savings$5,789

Estimate only. SE tax (IRC §1401) against FICA on the salary, 2026 wage base $184,500. Excludes income tax, §199A and California's 1.5% franchise tax. Open the full calculator

12free calculators
4Excel models
28,550formulas in the reporting package
1CPA doing the work

The calculator index

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-021099 Estimated Tax PlannerQuarterly federal and California estimates using the 90%, 100% or 110% safe harbor, with an option for uneven income.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 BUS-06True RunwayA cash forecast by month and by week under bad, base and good scenarios, with a reserve for taxes.Business owners IND-01Withholding CheckupCompares federal withholding to the estimated tax on your return and suggests a Form W-4 change.Individuals IND-02California Take-Home PayGross pay to net pay after federal tax, FICA, California tax and SDI.Individuals IND-03Itemize vs. Standard DeductionCompares itemized deductions with the standard deduction and uses the larger.Individuals IND-04Life-Event W-4 HelperA checklist of Form W-4 changes after a marriage, a new child, a home purchase or a side job.Individuals RE-01Rental Property AnalyzerNet operating income, cap rate, cash-on-cash return and debt service coverage for a rental property.Real estate DEBT-01Loan AmortizationPayment, total interest and a full schedule, with the savings from extra principal payments.Loans and debt

What I do

All services
SVC-TAX

Tax preparation and planning

1040 · 1120-S · 540 · 100S · An engagement letter Individual returns, sole proprietors and single-member LLCs, and S-corporation returns (Form 1120-S), with planning while decisions can still change the result. SVC-BKP

Accounting and monthly close

QuickBooks Online · Every month · Job costing Monthly accounting in QuickBooks Online, reconciliations, the close and financial statements, cleanups of books that have fallen behind, and job costing for contractors. SVC-SCO

S-corporation elections and entity setup

2553 · 2 mo. 15 days · 1.5% · $800 min Whether an S election makes sense at your profit level, the election itself, reasonable compensation, and the first-year setup that follows. SVC-RPT

Financial reporting and modeling

ASC 842 · 810 · 805 · 606 · BS · IS · CF · notes · SSARS AR-C 70 Financial statement packages, technical accounting (ASC 842, 810, 805, 606), opening balance sheets after an acquisition, cash forecasts and decision models.
Excel models

Built the way I build them for clients.

v2.1

Financial Reporting Package

21 tabs · 28,550 formulasv2.0

C-Corp to S-Corp Conversion Analyzer

12 tabs · 429 formulasv1.0

QSBS §1202 Analyzer

6 tabs · Founders, early employees and investors holding C-corporation stock

From the Knowledge Hub

All articles

C Corporations: The Extended California Form 100 Is Due Mid-November 2026

Business owners · California deadlines

Protecting Your Business's Tax and Payroll Records: Six Steps From the IRS

Business owners · Recordkeeping

Third-Quarter Form 941 Is Due November 2, 2026. What to Finish First

Business owners · Payroll

When the answer needs judgment, ask me.

Send a few sentences. If it fits, you get an engagement letter with the scope and fee, and the IRC §7216 consent forms. Documents go through the secure portal.

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