Quarterly Estimated Tax Planner

Quarterly Estimated Tax Planner Excel for freelancers, self-employed workers, and anyone paying estimated tax — income by quarter, a safe-harbor worksheet, a payments log, and an annual reconciliation with a next-year planner. Know what each quarterly payment should be, whether you paid it, and what is still owed at filing.

Built for self-employed and freelance workers who need to know, quarter by quarter, what the installment should be and whether they are on track — without accounting software. If a quarter was paid short, this workbook shows the shortfall and an estimated interest figure before the bill arrives.

WHAT'S INCLUDED (6 sheets):

- Quarterly Income Log — quarter, income description, income, withholding, and credits for each quarter. Totals feed the worksheet by formula.

- Estimated Tax Worksheet — estimated total tax, prior-year tax, safe-harbor percentage, the 90 percent test, the safe-harbor amount, required total payments, and the quarterly required payment. A second block shows the quarterly amount if you pay the full estimated tax instead.

- Payments Log — date paid, quarter, amount due, amount paid, shortfall, months late, interest rate, and estimated underpayment interest for each installment.

- Annual Reconciliation and Next-Year Planner — estimated total tax minus withholding, estimated payments, and credits (amount owed at filing), plus estimated interest and the total due with the return, and a next-year quarterly planner.

- Dashboard — income, withholding, credits, estimated tax, safe harbor, quarterly required payment, payments made, shortfall, interest, amount owed, total due, and next-year quarterly amount.

- Cover and How to Use — start here. Yellow cells are the only ones you edit.

EXAMPLE DATA (2026 tax year — replace with your own numbers):

- Income 120,000 (Q1 28,000, Q2 31,500, Q3 26,000, Q4 34,500); withholding 9,600; credits 1,500.

- Estimated total federal tax 26,500; prior-year (2025) tax 22,400; safe-harbor percentage 100 percent; 90 percent of current-year tax 23,850; safe-harbor amount 22,400; required total payments 22,400.

- Estimates needed 12,800; quarterly required payment 3,200; full-estimate quarterly amount 3,850 (650 more per quarter).

- Payments: Q1 3,200 on time; Q2 2,500 (700 short); Q3 3,200; Q4 3,900 (catch-up); total paid 12,800; total shortfall 700; estimated interest 28 (700 at 8 percent for 6 months).

- Amount owed at filing 2,600; plus estimated interest 28; total due with return 2,628.

- Next year (2027): estimated tax 28,000, withholding 10,400, credits 1,500, estimates needed 16,100, quarterly payment 4,025; safe-harbor check also 4,025 per quarter.

HOW IT WORKS:

1. Download the Excel file instantly after purchase.

2. On sheet 1, enter income, withholding, and credits for each quarter.

3. On sheet 2, enter your estimated total tax for the year and last year's total tax. The safe-harbor comparison and quarterly amount fill in by formula.

4. On sheet 3, enter each payment as you make it. A short quarter shows the shortfall and an estimated interest figure.

5. On sheet 4, the amount owed at filing fills in by formula, and the next-year planner gives you next year's quarterly amount.

HOW THE NUMBERS WORK:

Required total payments are the lesser of 90 percent of this year's estimated tax and the safe-harbor percentage of last year's tax. Estimated tax to pay in installments is required total payments minus withholding, divided by 4 for the quarterly required payment. Shortfall is amount due minus amount paid, or 0 when paid in full. Estimated interest is shortfall times the interest rate times months late divided by 12. Amount owed at filing is estimated total tax minus withholding minus estimated payments minus credits. Total due with the return is the amount owed plus estimated interest.

WHO IT'S FOR:

Freelancers, self-employed workers, gig workers, and anyone with income that has no withholding who wants quarterly payments, safe harbor, and the year-end bill in one workbook — without accounting software.

PLEASE NOTE:

- This is a digital download. No physical item will be shipped.

- Works in Microsoft Excel and Google Sheets (upload to Google Drive to open in Sheets).

- Example data for the 2026 tax year is included (income 120,000, withholding 9,600, credits 1,500, estimated total federal tax 26,500, prior-year tax 22,400). Replace it with your own numbers.

- The example is simplified: the Q2 installment was paid 700 short, which draws an estimated 28 of underpayment interest, and paying only the safe-harbor amount leaves 2,600 still owed at filing — safe harbor avoids the penalty, not the bill. Paying the full-estimate quarterly amount of 3,850 instead would have left nothing owed.

- All tax figures are planning estimates for the 2026 tax year (returns filed in 2027). Safe-harbor rules, due dates, and interest rates change — confirm them with your own accountant or CPA before filing or paying.

- This is a planning tool only, not tax, legal, or CPA advice.

- Due to the nature of digital downloads, refunds are not available. Message me before buying if you have a question.

Built by an accountant: B.S. Accountancy, ASU W. P. Carey, with revenue-reconciliation experience at Marriott and audit work at PwC.