Next federal deadline Jan 15 in 109 days

Safe harbor and annualized income for the whole book

Each estimate comes with the Form 2210 Schedule AI, the quarterly report, and the filled 1040-ES vouchers.

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Free for one client. The report, vouchers and Schedule AI start with Plus. No card, no password.

Q4 2026 · client estimates

0 of 6 ready for review

Due Jan 15

Alvarez, M.

S-corp owner · married filing jointly

Chen Household

Schedule C · married filing jointly

Kowalski, R.

Partnership K-1 · single

Reyes, D.

W-2 + RSU sales · single

Needs Q4 figures

Through Q3 on file

Nakamura, K.

Consultant + rental · head of household

Okafor, T.

Attorney, contingency fees · married filing jointly

Sample book. Figures from the 2026 engine.

Built on the IRS's own rules

Form 1040-ESIRC §6654Form 2210Schedule AIPublication 505Form 8582Rev. Proc. 2025-32

Built for the quarterly crunch. It replaces the spreadsheet, not your judgment.

Safe harbor and the annualized income installment method, compared.

Q4 requirement by method

Safe harbor Annualized

Alvarez, M.

S-corp owner

$3,574.20

$21,293.00 under safe harbor

Chen Household

Schedule C

$5,883.96

$5,333.00 under safe harbor

Kowalski, R.

Partnership K-1

$19,855.40

$5,203.00 under safe harbor

Nakamura, K.

Consultant + rental

$3,802.00

Safe harbor is lower

Okafor, T.

Attorney, contingency fees

$7,370.00

Safe harbor is lower

3 of 5 pay less under the annualized income method this quarter. Each one gets the Schedule AI that proves it. Book total $40,485.56

Schedule AI, produced for each client

Form 2210 with all four periods, from the same calculation.

Client-ready PDFs

The quarterly report and the filled 1040-ES voucher, ready to send or attach to your letter.

Q4 report · Chen Household

Ready

1040-ES voucher · Chen Household

Ready

State safe harbor for every client, cited to the 2025 return line.

California

Three payments, 30 / 40 / 0 / 30 by quarter, on 110% of last year's state tax of $12,400.00.

2025 Form 540, lines 48, 61, and 62 added together

Q1 Apr 15

$4,092.00

Q2 Jun 15

$5,456.00

Q3 Sep 15

none

Q4 Jan 15

$4,092.00

42 state returns cited by line. The state figure is the safe harbor, not a full state calculation.

Audit every line before you sign off. Every figure names its code section or form line.

Income, deductions, tax, both requirements, and the installment, with the source beside each one. A verification suite built on the official IRS documents, Rev. Proc. 2025-32, Forms 1040-ES and 2210, and the SSA wage base, checks every constant in the engine.

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Alvarez, M. · 2026 worksheet

S-corp owner · married filing jointly · sample

Owner W-2 wages through Dec 31 W-2 box 1
$96,000.00
S-corp ordinary income through Dec 31 Schedule K-1 box 1
$118,000.00
Annualized, × 1 for the period Schedule AI lines 1 to 3
$214,000.00
Adjusted gross income Form 1040 line 11a
$214,000.00
Standard deduction, married filing jointly IRC §63(c)
−$32,200.00
Qualified business income deduction IRC §199A
−$23,600.00
Taxable income IRC §63(a)
$158,200.00
Federal income tax IRC §1
$24,228.00
Total tax, annualized Form 1040 line 24
$24,228.00
Annualized requirement, 90% IRC §6654(d)(2)
$21,805.20
Safe harbor, 110% of 2025 tax IRC §6654(d)(1)(C)
$43,098.00
Withholding credited by the Q4 due date IRC §6654(g)
−$14,800.00
Paid Q1 to Q3 Form 1040-ES vouchers
−$3,431.00
Q4 installment, annualized Due Jan 15
$3,574.20

Sample calculation from the 2026 engine. Amounts are annualized figures under the annualized income method, Schedule AI column for the period ending Dec 31.

Flat tiers sized by the book. No per-client fee, and the engine is the same on every plan.

A bigger plan buys client capacity, never a better calculator. Worksheet mode comes with every plan, Free included. Both practice plans include the client dashboard, the quarterly PDF report, filled 1040-ES vouchers, and the Form 2210 package for every client.

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Up to 10 clients

$49/ quarter

billed $196/year, or $69 billed quarterly

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Client management dashboard
PDF reports & filing packages for every client

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Client management dashboard
PDF reports & filing packages for every client

Quarterly estimates for the whole book. Start with one client.

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Free for one client. The report, vouchers and Schedule AI start with Plus. No card, no password.