Fourth and final quarterly estimated tax payment, due January 15 of next year.
The Q4 estimated tax payment covers October–December income and is due January 15 of the following year. This is the final quarterly payment, and your last chance to "true up" your estimated tax liability before filing your full return on April 15.
By January 15, you have complete data for the prior calendar year. Many people pay their Q4 estimate based on actual income through December, then file their return in early April once all documents are received. This approach minimizes the risk of overpayment or underpayment penalties.
If you have substantial self-employment income, consider paying your Q4 estimate promptly after January 1 rather than waiting until January 15. This ensures you don't miss the deadline while dealing with holiday schedules or travel.
Underpaying estimated taxes results in:
- Underpayment penalty, though now limited to Q4
- Interest on unpaid amount through April 15 tax filing
Add this deadline to your phone, calendar, or reminder app 2–3 weeks in advance to avoid last-minute stress.