Quarterly Tax Safe Harbor Calculator
The exact quarterly payment to avoid the IRS underpayment penalty. Enter your prior year tax and current year income — we compute both safe harbor methods and recommend the lower one with a per-quarter payment schedule.
Safe harbor = the exact payment to avoid the underpayment penalty
Two methods qualify. The IRS lets you choose whichever requires less. This calculator computes both and recommends the lower one.
Prior year tax return
Find these on your prior year Form 1040: total tax (line 24) and AGI (line 11).
Current year income estimate
Used to calculate Option B (90% of current year tax). Leave SE income at $0 if not applicable.
Option A
Prior Year Tax Method
$8,000
100% of prior year tax ($8,000)
Source: IRS Pub 505, IRC §6654(d)(1)(B)(ii)
Option B
90% Current Year Method
$17,551
90% of estimated $19,501 current year tax
Source: IRC §6654(d)(1)(B)(i)
Payment schedule (equal installment method)
Q1
$2,000
Due April 15
Jan 1 – Mar 31
Q2
$2,000
Due June 15
Apr 1 – May 31
Q3
$2,000
Due Sep 15
Jun 1 – Aug 31
Q4
$2,000
Due Jan 15
Sep 1 – Dec 31
Note on unequal quarters: Q2 covers only 2 months while Q4 covers 4 months — yet both receive the same payment under the standard equal installment method. If your income is seasonal (earned mostly in Q1 or Q4), consider Form 2210 Annualized Income Installment Method, which can reduce penalties for uneven income.
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