Quarterly Estimated Taxes: Safe Harbors and Due Dates

TaxKiln Editorial · Last reviewed: May 25, 2026

Self-employed taxpayers, owner-operators, and investors with significant non-wage income generally pay federal tax in four quarterly instalments using Form 1040-ES. To avoid the §6654 underpayment penalty, total withholding plus estimated payments must equal at least 100% of last year's total tax (110% if prior-year AGI > $150,000) or 90% of current-year tax — whichever is less. Due dates are April 15, June 15, September 15, and January 15.

Who is required to pay quarterly

Anyone who expects to owe at least $1,000 in federal tax after withholding and refundable credits. Common profiles: sole proprietors, single-member LLCs, partners, S-corp shareholders, gig workers, landlords, traders, retirees with large RMDs, and W-2 employees with significant side income or capital gains.

The two safe harbours

**Prior-year safe harbour** — total withholding + estimated payments ≥ 100% of last year's total tax (110% if prior-year AGI > $150,000, or > $75,000 MFS). This is the planning-stability favourite: the target is fixed once last year's return is filed. **Current-year safe harbour** — total payments ≥ 90% of current-year total tax. Useful when current income is dropping; lets you avoid prepaying based on an inflated prior year. The penalty calculation uses whichever target is lower — you only need to clear one.

Annualized income method (Form 2210 Schedule AI)

If income is lumpy across the year (a Q4 commission, a single capital gain, a project that started in July), the standard "25% of total per quarter" formula can over-penalise. The annualized income instalment method lets you allocate income to the quarter it was actually earned, smoothing the underpayment calculation. It is more compliance work but often eliminates a §6654 penalty.

How to pay

IRS Direct Pay (free, ACH from bank), EFTPS (free, ACH; ideal for businesses), debit/credit card via approved processors (fees apply), or paper voucher mailed with Form 1040-ES. EFTPS is the most reliable channel for recurring quarterly payments.

State estimated tax

Most states with an income tax run their own estimated-tax regime. Due dates often mirror federal (Apr 15 / Jun 15 / Sep 15) but state-specific Q4 dates may differ (Jan 15 in many states, but some use other dates). Each state publishes its own safe-harbour rules and forms.

Worked example: Renee Kim, S-corp owner-operator (Denver, CO)

Renee's 2025 total federal tax was $42,000 (AGI was $185,000). She expects 2026 income to be similar. No W-2 withholding because she pays herself only quarterly estimated.

Prior-year safe harbour (AGI > $150,000): 110% × 42,000 = 46,200 Quarterly target: 46,200 / 4 = 11,550 per quarter Due Apr 15: 11,550 · Jun 15: 11,550 · Sep 15: 11,550 · Jan 15 (2027): 11,550 If she pays these four instalments timely, no §6654 penalty applies regardless of 2026 actual tax.

Statute references

Underpayment of estimated tax by individuals — IRC §6654
Prior-year and current-year safe harbours — IRC §6654(d)
Annualized income instalment method — IRC §6654(d)(2)

Last reviewed: May 25, 2026