Glossary
Quarterly estimated tax
Payments made four times a year on income that has no tax withheld from it.
Income tax in the United States is pay-as-you-go. Where an employer withholds, that happens automatically; where it does not — freelance work, gig platforms, creator payouts, investment income — the IRS expects payments across the year using Form 1040-ES. The four periods do not divide the calendar evenly, and the fourth payment falls in January of the following year. Underpaying can trigger a penalty even when the balance is settled in full at filing, which is what the safe-harbor rules exist to prevent.