Estimated taxes
Quarterly estimated tax checklist
An estimated tax payment is only as good as the income projection behind it. The firm needs the current-year income so far, the withholding already taken, the payments already made and the safe-harbor rule the client is using. This checklist covers what to collect before each quarterly payment, for the federal return and for each state the client files.
Who sends itSent by the tax preparer to a client who pays estimated tax, such as a self-employed client, an S corporation owner or a client with investment income, before each quarterly due date.
0 of 17 ticked
01Income and withholding so far
02Payments already made
03The safe-harbor calculation
04Before the payment is sent
What firms get wrong
- Using last year's payment amount without checking whether the client's income changed.
- Forgetting withholding from wages or retirement distributions when calculating the payment.
- Missing a state estimated payment because only the federal date was on the calendar.
- Paying the prior-year safe-harbor amount without checking the higher percentage for higher-income clients.
- Waiting until the due date to ask for the year-to-date income, when there is no time to calculate the payment.
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Questions about this checklist
Who has to pay estimated tax?
A client generally needs to pay estimated tax when the tax withheld from wages and other payments is not enough to cover the tax owed. Self-employed clients, S corporation owners and clients with large investment income are common examples.
When are estimated tax payments due?
Federal estimated payments are generally due April 15, June 15, September 15 and January 15 of the following year. When a date falls on a weekend or holiday, it moves to the next business day. State dates can differ.
What is the safe harbor?
A client can generally avoid an underpayment penalty by paying at least 90% of the current-year tax or 100% of the prior-year tax, with a higher percentage for higher-income taxpayers. The firm should calculate both methods before choosing a payment.
What if the client's income is seasonal?
The annualized income installment method may reduce or delay a payment for a client whose income arrives in one part of the year. It requires the income and deductions for each period, so ask for the records by quarter.
Can the client skip a payment and catch up later?
Skipping a payment can create an underpayment penalty for that period even if the client pays more later. The firm should calculate the penalty exposure before deciding to skip or reduce a payment.
Sources
- IRS: Estimated taxes
- IRS: About Form 1040-ES
- IRS: Publication 505, Tax Withholding and Estimated Tax
Checked November 3, 2026. Tax rules, forms and thresholds change; confirm them with the IRS or your tax software before relying on them.
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