This tool uses UK context.
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Money · Quarterly tax check
US Quarterly Tax Threshold
When does side income trigger estimated quarterly taxes? The most common costly mistake among new freelancers — and what the penalty actually costs.
Instant result
Plain-English why
Copyable takeaway
What this means
No waffle. Just the number and how it was worked out.
Formula used
Quarterly payment = ((side_income × self_employment_tax_rate) + (total_income - standard_deduction - w2_withholding_estimate) × marginal_rate) / 4
Worked example
A freelancer earning $60,000 W-2 plus $20,000 side income in a 22% bracket owes roughly $2,800 per quarter in estimated taxes — and faces a ~8% underpayment penalty if they miss all four payments.
Common questions
When do I have to pay estimated quarterly taxes?
If you expect to owe $1,000 or more in federal taxes beyond what is withheld from your W-2, you are generally required to pay estimated quarterly taxes. Missing these triggers an underpayment penalty.
What is the self-employment tax?
Self-employment tax covers Social Security (12.4%) and Medicare (2.9%) — a total of 15.3% — on net self-employment income. As a self-employed person, you pay both the employer and employee halves.
Plain-English summary
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This section translates the result into a short, direct takeaway rather than leaving the page at a bare number.
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