Quarterly Estimated Taxes.
Set It and Forget It.

If you underpay your estimated taxes, the IRS may charge you an underpayment penalty, which is calculated as interest on the amount you should have paid. However, you can avoid penalties if you meet the safe harbor rules mentioned above, or if your total withholding and estimated tax payments equal at least 90% of your current year tax liability.

The IRS has four payment deadlines each year: April 15 (for January-March income), June 15 (for April-May income), September 15 (for June-August income), and January 15 of the following year (for September-December income). If a deadline falls on a weekend or holiday, the due date moves to the next business day.

Yes, you can adjust your estimated tax payments each quarter based on your actual income. If your income increases or decreases significantly during the year, you should recalculate your estimated taxes to avoid underpayment penalties or overpaying. The IRS allows you to use the "annualized income installment method" if your income is uneven throughout the year, which can help you pay the right amount each quarter based on when you actually earned the income.

You can pay your quarterly estimated taxes several ways: electronically through IRS Direct Pay or EFTPS (Electronic Federal Tax Payment System), by credit or debit card through an IRS-approved payment processor, by mailing a check or money order with Form 1040-ES payment voucher, or through your tax professional. The IRS encourages electronic payments as they're faster, more secure, and provide immediate confirmation. Many states also require quarterly estimated tax payments, so check your state's tax agency website for payment options and deadlines.