The third quarter estimated tax payment deadline is September 16, 2024. If your income has been higher than expected this year, or if you had a large capital gain, a bonus, or strong business revenue in Q3, now is the time to recalculate. Underpayment penalties at the current 8% IRS rate add up quickly. Here are three strategies to stay ahead.
Strategy 1: Use the Safe Harbor
The simplest way to avoid underpayment penalties is the safe harbor rule: pay at least 100% of your prior year’s total tax liability through withholding and estimated payments (110% if your AGI exceeded $150,000). Even if you owe significantly more when you file, meeting the safe harbor means no penalty. This works best when your income is growing but you do not want to precisely calculate each quarter’s liability.
Strategy 2: Annualize Your Income
If your income is uneven, perhaps concentrated in one quarter due to a large sale, bonus, or seasonal business cycle, you can use the annualized income installment method (Form 2210, Schedule AI). This calculates your required payment based on income actually received in each period rather than assuming even distribution across the year. It requires more work but can significantly reduce required payments in quarters where your income was lower.
Strategy 3: Adjust Withholding on W-2 Income
If you have W-2 income from employment in addition to your business income, increasing your payroll withholding is one of the most effective tools. Withholding is treated as if it were paid evenly throughout the year, even if the extra withholding happens entirely in Q4. This means you can “catch up” on estimated payments by bumping up your withholding for the final months of the year. Submit a new W-4 to your employer with reduced allowances or a specific additional withholding amount.
The Cost of Underpaying
At the current 8% annual rate, the underpayment penalty is calculated daily on the shortfall for each quarter. On a $10,000 underpayment for one quarter, the penalty is approximately $200. That compounds across multiple quarters of underpayment. It is not catastrophic, but it is entirely avoidable with proper planning.
If you have not made your Q3 payment yet, calculate your year-to-date income and payments, compare against the safe harbor, and make a payment through IRS Direct Pay or EFTPS before the deadline. A few minutes of calculation can save you hundreds in penalties.