Safe Harbor Tax Calculator

What the safe harbor is

The US tax system is pay-as-you-go, so the IRS expects you to pay tax throughout the year, not just at filing. If you underpay, you can owe an underpayment penalty. The "safe harbor" is a guaranteed way to avoid that penalty: pay at least a defined minimum and you are protected even if you end up owing more at tax time.

The two safe-harbor tests

You meet the safe harbor if your withholding plus estimated payments total at least the smaller of these two amounts:

• 90% of this year's tax - useful when your income is falling, but it depends on an estimate.
• 100% of last year's tax - or 110% if your prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately). This is a known number, so it is the target most freelancers use.

How withholding fits in

Taxes withheld from a W-2 job or other source count toward the safe harbor and are treated as paid evenly across the year. That is why this calculator subtracts your withholding first and splits only what is left into four equal estimated payments. If withholding alone already covers the target, you may not need estimated payments at all.

When you can skip estimated payments

If you expect to owe less than $1,000 for the year after withholding and credits, you generally do not need to make estimated payments. Above that, missing the safe harbor risks a penalty that works like interest on the shortfall. Once you know your target, the quarterly tax calculator and our quarterly estimated taxes guide walk through the four due dates and how to pay the IRS.