How we figure it · Tax Pit Stop

How we round

Money you owe or set aside rounds up to the next dollar.
Deductions and savings round down.
With only a few weeks of payouts, we plan for a busy year until there’s more to go on.
When we’re not sure about something, we leave it out rather than guess.

The 2026 tax year

Income tax brackets: Rev. Proc. 2025-32 §4.01; 2026 Form 1040-ES, 2026 Tax Rate Schedules
Standard deduction: Rev. Proc. 2025-32 §4.14(1); 2026 Form 1040-ES, What's New
Self-employment tax: 2026 Form 1040-ES, Self-Employment Tax and Deduction Worksheet; Pub 505 (2026) Worksheet 2-3
Extra Medicare tax on high pay: Pub 505 (2026) ch. 2, Additional Medicare Tax chart
Business income deduction: Rev. Proc. 2025-32 §4.26 and §2.12; 2026 Form 1040-ES, What's New
No tax on tips: 2026 Form 1040-ES, What's New (No tax on tips); 2025 Schedule 1-A lines 9-13 for the reduction steps
IRS mileage rate: Notice 2026-10 (IR-2025-128); Announcement 2026-11, IRB 2026-29 (IR-2026-29); irs.gov standard mileage rates table (Jan. 1 - June 30 and July 1 - Dec. 31, 2026), checked 2026-10-09
The smallest payments that avoid a penalty: Pub 505 (2026) ch. 2; 2026 Form 1040-ES Estimated Tax Worksheet lines 12a-14b
Quarterly due dates: 2026 Form 1040-ES, Payment Due Dates; Pub 505 (2026) Table 2-1 and Worksheet 2-12
Skipping the January payment: 2026 Form 1040-ES, Payment Due Dates footnote
The penalty for paying late: IRS quarterly interest rates (IRB 2026-08, 2026-22, 2026-36); periods laid out as in the 2025 Form 2210 instructions
Child tax credit: Rev. Proc. 2025-32 §4.05; 2026 Form 1040-ES (What’s New; worksheet lines 7 and 11b); other amounts from the 2025 Schedule 8812 (see VERIFY)
States with no income tax: Tax Foundation, State Individual Income Tax Rates and Brackets, 2026; each state’s revenue department
State due dates and payment sites: CA: 2026 Form 540-ES instructions (ftb.ca.gov); NY: Form IT-2105-I (2026); IL: Form IL-1040-ES (2026); PA: 2026 REV-413 (I) Instructions for Estimating PA Personal Income Tax (pa.gov; at least $430, the tax on $14,000 of income not subject to withholding at 3.07%); OH: tax.ohio.gov Estimated Payments page (more than $500; 2026 due dates; read 2026-10-10); GA: Form 500-ES; NC: ncdor.gov Estimated Income Tax page ($1,000 or more; see VERIFY); MI: Form MI-1040ES (2026); NJ: Form NJ-1040-ES (2026); VA: 2026 Form 760ES, Rev. 09/25 (more than $1,000; first date May 1); AZ: Form 140ES (2026); WI: Form 1-ES (2026); CO: Form DR 0104EP (2026); MN: Form M14 / revenue.state.mn.us estimated tax page
Line numbers in the tax-time pack: Copied from the 2025 forms (2025 Schedule C, Schedule SE, Schedule 1-A, Form 1040) until the 2026 forms are published
Where last year’s numbers are on your return: 2025 Form 1040 lines 11a and 24

The 2025 tax year

Income tax brackets: Rev. Proc. 2024-40 §3.01; 2025 Form 1040 instructions, Tax Computation Worksheet
Standard deduction: 2025 Form 1040 instructions, What's New (OBBBA amounts)
Self-employment tax: Pub 334 (2025) ch. 10; 2025 Form 1040-ES SE worksheet; 2025 Schedule SE instructions
Extra Medicare tax on high pay: 2025 Form 8959 instructions
Business income deduction: Rev. Proc. 2024-40 §3.27; 2025 Form 8995 instructions
No tax on tips: 2025 Schedule 1-A lines 7-13 and its instructions (Part II)
IRS mileage rate: Notice 2025-5 (IR-2024-312)
The smallest payments that avoid a penalty: Pub 505 ch. 2; 2025 Form 1040-ES worksheet; 2025 Form 2210 instructions
Quarterly due dates: 2025 Form 1040-ES, Payment Due Dates
Skipping the January payment: 2025 Form 1040-ES, Payment Due Dates footnote
The penalty for paying late: 2025 Form 2210 instructions, Penalty Worksheet (Rate Periods 1-4); IRS quarterly interest rates (IRB 2025-13, 2025-23, 2025-37, 2025-48)
Child tax credit: 2025 Schedule 8812 lines 5-20 and its instructions (Credit Limit Worksheet A, Earned Income Worksheet)
States with no income tax: Tax Foundation, State Individual Income Tax Rates and Brackets, 2026; each state’s revenue department
State due dates and payment sites: None listed: every 2025 state due date has passed
Line numbers in the tax-time pack: 2025 Schedule C (lines 1-31, Part IV lines 43-44); 2025 Schedule SE line 2; 2025 Schedule 1-A lines 5 and 13; 2025 Form 1040 line 26
Where last year’s numbers are on your return: 2024 Form 1040 lines 11 and 24 (irs.gov/pub/irs-prior/f1040--2024.pdf)

Still being double-checked

Some figures come out before the IRS prints the form they go on, or sources disagree. We list them here. Until each is confirmed, the app uses the value that gives the higher tax.

2026 · No tax on tips. The $100-per-$1,000 reduction is copied from the 2025 Schedule 1-A. Confirm it on the 2026 Schedule 1-A when published (the law sets it for 2025-2028).
2026 · No tax on tips. Same as above: from the 2025 Schedule 1-A.
2026 · Business income deduction. New for 2026 (Rev. Proc. 2025-32 §2.12). The 2026 Form 8995 is not out yet. The app applies the $400 minimum but never lets it push taxable income below zero; confirm that against the 2026 form.
2026 · Business income deduction. Secondary sources disagreed on the married-filing-separately amount; Rev. Proc. 2025-32 §4.26 says $201,775 (MFS) and $201,750 (all other). Worth a second look.
2026 · Extra Medicare tax on high pay. Taken from Pub 505 (2026); the 2026 Form 8959 instructions are not out yet. These amounts are fixed by law (not inflation-adjusted).
2026 · Self-employment tax. The $400 floor is from Pub 505 (2026) Worksheet 2-3 and the 2025 Schedule SE instructions; the 2026 Schedule SE is not out yet.
2026 · Line numbers in the tax-time pack. Line numbers are from the 2025 forms. Check each one on the 2026 Schedule C, Schedule SE, Schedule 1-A and Form 1040 when they come out (late 2026 to January 2027); lines sometimes move.
2025 · Line numbers in the tax-time pack. The app puts a phone used for gig work on line 25 (Utilities). The Schedule C instructions talk about home phone lines but do not name cell phones; listing it under Other expenses (line 27b, Part V) is also common. The total profit is the same either way.
2026 · The penalty for paying late. The rate for January 1 - April 15, 2027 is not announced yet (the IRS sets it in late November). The app uses 7%, the highest 2026 rate. Check irs.gov/payments/quarterly-interest-rates, and the 2026 Form 2210 instructions when they come out.
2026 · Child tax credit. The $2,200 and $1,700 are from Rev. Proc. 2025-32. The $500 credit for other dependents, the $200,000 / $400,000 phase-out (5 percent per $1,000), the $2,500 floor and the 15 percent are set by law and copied from the 2025 Schedule 8812; confirm them on the 2026 Schedule 8812. The app leaves out Part II-B (a larger refundable credit some families with 3 or more children get), so it can run high for them.
2026 · State due dates and payment sites. State rules are copied from each state’s 2026 estimated tax instructions (sources in CITATIONS). States are not IRS figures and change their forms each year: re-check each state when its 2027 form comes out.
2026 · State due dates and payment sites. North Carolina’s $1,000-or-more rule is from the Department of Revenue’s estimated income tax page (read 2026-10-10); the 2026 NC-40 instructions were not online yet to confirm it on the form itself.
2026 · States with no income tax. From the Tax Foundation’s 2026 table, not each state’s own page. Worth a look at each state’s revenue site.
2025 · Standard deduction. OBBBA raised these after Rev. Proc. 2024-40; copied from the 2025 Form 1040 instructions.

What we leave out

These can lower your tax, but we don’t count them yet. Leaving them out keeps your number on the safe side:

other tax credits, like the earned income credit or the child care credit
itemized deductions
other income such as interest or investments
health insurance and retirement deductions for the self-employed

We don’t prepare or file tax returns. Your tax software or tax preparer works out the final amount.

A planning estimate, not tax or financial advice.