Calcufast

Estimated tax safe harbor: $10,000 prior tax → $1,000/quarter

IRC 6654: pay 100% of last year’s tax (110% if AGI was over $150,000) minus withholding, divided by 4.

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Results

Payment per quarter

$1,000.00

Required annual (safe harbor)

$10,000.00

Still to pay via 1040-ES

$4,000.00

IRC 6654 100%/110% harbor only. Does not model 90% of current-year tax, MFS $75,000, or farmers. Educational estimate, not tax advice.

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1040-ES safe harbor

IRC 6654 lets you avoid an underpayment penalty by paying 100% of last year’s tax (110% if prior-year AGI was over $150,000), minus withholding.

Quarterly

quarterly = max(0, prior-year tax × rate − withholding) / 4

Example: $10,000 prior tax, $6,000 withholding → $1,000 per quarter. If AGI was over $150,000: $11,000 − $6,000 = $5,000 → $1,250 per quarter.

Related: paycheck take-home, federal withholding.