Tax source policy
Tax Source Verification Policy
Visible assumptions before tax math.
Kefiw tax tools are educational planning calculators. They should help operators ask better questions, protect cash, and audit assumptions without pretending a calculator is a tax filing position.
Required Tax footer
Last source check: April 30, 2026. Tax rules, thresholds, forms, deadlines, and state rules can change. Kefiw shows the assumptions used so you can audit the math before relying on the result. Tax calculators do not provide legal, tax, accounting, payroll, or filing advice.
What gets source checked
Self-employment and estimated tax tools
- IRS self-employment tax framing and Form 1040-ES planning references
- Social Security wage base and Medicare assumptions
- Payment-period, safe-harbor, withholding, and uneven-income caveats
- Federal-only default unless a state reserve assumption is entered
Deduction and documentation tools
- IRS business-expense resource guidance instead of stale Publication 535-only citations
- Schedule C, mileage, home-office, documentation, mixed-use, and capitalization prompts
- Explicit wording that the tool flags caution issues and does not approve deductions
S-corp and reasonable salary tools
- IRS reasonable-compensation and officer wage treatment guidance
- Payroll, filing, bookkeeping, state/entity, and admin-cost placeholders
- Explicit wording that the tool does not determine reasonable salary or tax election status
Wording rules
- Call outputs estimates, planning scenarios, reserve targets, or model results.
- Do not call a calculator result a tax bill, filing position, guaranteed penalty result, or professional determination.
- Show assumptions that can move the result: wage base, income timing, withholding, payments, salary, payroll cost, filing cost, records, and state assumptions.
- Make "what this tool does not do" visible on high-risk tax calculators.
- Use the current source-check date on Tax calculators: April 30, 2026.
Current tax calculator source packs
Each high-risk tax tool carries a source scope, assumptions, visible caveats, and links to source families used by the calculator.
Self-Employed Tax Calculator
Last source check: April 30, 2026
U.S. federal self-employment tax, Social Security wage base, and federal income-tax planning defaults. State tax is only a user-entered reserve assumption.
Assumptions shown
- Uses 92.35 percent net earnings framing, 12.4 percent Social Security up to the 2026 taxable maximum, and 2.9 percent Medicare.
- Does not replace tax advice or full Form 1040-ES worksheets.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Quarterly Tax Estimate Calculator
Last source check: April 30, 2026
U.S. federal estimated-tax due dates, safe-harbor framing, Form 1040-ES, Publication 505, and uneven-income caveats.
Assumptions shown
- Estimated tax rules are pay-as-you-go and depend on prior-year safe harbor rules.
- Use official Form 1040-ES or a tax professional before sending payments.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Tax Reserve Health Score
Last source check: April 30, 2026
U.S. federal self-employment tax, Form 1040-ES estimated-tax planning, payment-period framing, and user-entered state reserve assumptions.
Assumptions shown
- This is a planning score for tax reserve behavior, not a tax filing position.
- State reserve is a user-entered placeholder unless reviewed separately.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Quarterly Tax Catch-Up Calculator
Last source check: April 30, 2026
IRS estimated-tax payment periods, Form 1040-ES planning, Publication 505, and annualized-income caveats for uneven income.
Assumptions shown
- This estimates a catch-up plan, not an underpayment penalty.
- Uneven income may need annualized-income review using IRS forms and professional guidance.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Mixed W-2 + 1099 Tax Planner
Last source check: April 30, 2026
Federal self-employment tax, withholding interaction, Form 1040-ES planning, and user-entered income-tax reserve assumptions.
Assumptions shown
- W-2 withholding may help cover the total household tax picture, but timing and withholding updates matter.
- This is a planning model, not a completed Form 1040.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Irregular Income Tax Reserve Planner
Last source check: April 30, 2026
Federal estimated-tax payment rhythm, annualized-income caveat, self-employment tax baseline, and user-entered reserve assumptions.
Assumptions shown
- Uneven income may need annualized-income review; this tool only builds a cash reserve plan.
- High-income months should move tax reserve immediately before the cash starts looking available.
Source links
- IRS Topic 554, Self-employment tax
- IRS Publication 334, Tax Guide for Small Business
- IRS 2026 tax inflation adjustments
- IRS estimated taxes for small business
- IRS estimated tax FAQ for individuals
- IRS Form 1040-ES estimated tax
- IRS Publication 505, Tax Withholding and Estimated Tax
- IRS Form 2210 underpayment and annualized income
- IRS payment options and payment plans
- SSA 2026 taxable maximum
Self-Employed Deduction Finder
Last source check: April 30, 2026
IRS business-expense resource guide, Schedule C instructions, 2026 mileage rate, and simplified home-office guidance.
Assumptions shown
- Uses the 2026 standard business mileage rate for mileage estimates.
- Deductibility depends on business purpose, substantiation, and tax facts.
Dangerous Deduction Checker
Last source check: April 30, 2026
IRS business-expense resource guide, Schedule C instructions, 2026 mileage rate, and simplified home-office guidance.
Assumptions shown
- This flags substantiation risk, not audit odds.
- If a deduction is large, mixed-use, or unusual for the business, document the business purpose.
Deduction Documentation Scorecard
Last source check: April 30, 2026
IRS business-expense resource guidance, Schedule C instructions, mileage records, home-office support, and capitalization review prompts.
Assumptions shown
- This scores record strength, not deductibility.
- Mixed-use, large, unusual, or asset-like expenses may need professional review even with records.
LLC vs S-Corp Calculator
Last source check: April 30, 2026
IRS S-corp reasonable-compensation guidance, federal payroll baseline, and Social Security wage base. State fees are user-entered assumptions.
Assumptions shown
- S-corp owners generally need a reasonable salary before distributions.
- This is a planning estimate, not entity-selection advice.
S-Corp Tax Savings Calculator
Last source check: April 30, 2026
IRS S-corp reasonable-compensation guidance, federal payroll baseline, and Social Security wage base. State fees are user-entered assumptions.
Assumptions shown
- Savings can disappear if salary is understated, admin cost is high, or state taxes offset the benefit.
- Reasonable salary is a facts-and-circumstances issue.
S-Corp Break-Even Stress Test
Last source check: April 30, 2026
IRS S-corp reasonable-compensation guidance, officer wage treatment, federal payroll baseline, Social Security wage base, and user-entered state/admin assumptions.
Assumptions shown
- The break-even point is an administrative threshold as much as a tax number.
- If savings disappear in stress tests, the entity may be too early even if the expected case looks good.
Reasonable Salary Planner
Last source check: April 30, 2026
IRS S-corp reasonable-compensation guidance and federal payroll baseline. This planner creates salary assumptions, not a legal salary determination.
Assumptions shown
- Use market pay, role scope, hours, skill level, and business facts to support salary.
- Do not use this as a substitute for CPA advice.
Update rhythm
Tax source checks should be refreshed when IRS or SSA thresholds change, forms are revised, due-date guidance changes, deduction documentation guidance changes, S-corp compensation guidance changes, or a calculator adds a new tax assumption.