Who has to pay
Generally, you should make estimated payments if you expect to owe $1,000 or more when you file, and your withholding won't cover it. That typically includes self-employed people, farmers, landlords, contractors receiving 1099-NEC income, and anyone with meaningful investment or side income.
The safe-harbor rules (your penalty protection)
You avoid an underpayment penalty if your combined withholding and estimated payments reach either:
- 90% of this year's tax, or
- 100% of last year's tax — 110% if your prior-year adjusted gross income was over $150,000.
For most people with rising income, the prior-year safe harbor is the simplest strategy: divide last year's total tax by four, pay it on schedule, and settle the difference in April — penalty-free.
When payments are due
| Payment | Covers income earned | Due |
|---|---|---|
| Q1 | Jan 1 – Mar 31 | April 15 |
| Q2 | Apr 1 – May 31 | June 15 |
| Q3 | Jun 1 – Aug 31 | September 15 |
| Q4 | Sep 1 – Dec 31 | January 15 (next year) |
Note the uneven periods — Q2 covers only two months. Deadlines falling on weekends or holidays move to the next business day. Special rules exist for farmers and fishermen, who can often pay once by January 15 instead — common in Northwest Iowa, and worth asking about.
How to actually pay
- Federal: IRS Direct Pay (bank transfer, free), EFTPS, or by mailing a check with a Form 1040-ES voucher.
- Iowa: pay online through GovConnectIowa or with Iowa's IA 1040-ES vouchers.
- Keep confirmation numbers — payments occasionally get misapplied, and proof settles it in minutes.
Want your quarterly numbers done for you?
Estimated-payment calculations are included in our small-business return service — we hand you the amounts and the vouchers, you just pay them.
Schedule Your Free 20-Min CallThis page is general information, not tax advice. Thresholds and safe-harbor percentages are set by federal and Iowa law and can change; confirm current-year rules at irs.gov or ask us.