Quarterly Estimated Taxes: A Calendar and a Checklist

Employees have taxes withheld invisibly. The self-employed pay in four explicit installments, and the penalty for skipping them is an interest charge that compounds quietly. The system is manageable once you see the whole year.

The calendar

• Q1 (income Jan 1 - Mar 31): due April 15
• Q2 (income Apr 1 - May 31): due June 15 (yes, only two months)
• Q3 (income Jun 1 - Aug 31): due September 15
• Q4 (income Sep 1 - Dec 31): due January 15 of the next year

How much to send

Two safe harbors keep you penalty-free: pay at least 90% of this year's eventual tax, or 100% of last year's tax (110% if your prior-year AGI topped $150k). The second is the planning-friendly one, divide last year's total tax by four and schedule it.

If this year is running well ahead of last year, estimate from actuals instead: year-to-date profit from your P&L × your combined rate (income tax bracket plus ~15.3% self-employment tax on net earnings), your CPA can pin the multiplier.

The quarterly ritual

• Categorize the quarter's transactions (rules should make this minutes).
• Run the P&L for the period, profit, not revenue, is the tax base.
• Apply your rate or safe-harbor number.
• Pay at IRS Direct Pay (and your state's equivalent, most states run parallel schedules).
• Move on with your life until the next date.

The deeper habit: transfer a fixed percentage of every payment you receive into a tax savings account the day it arrives. The quarterly payment then becomes a transfer, not a crisis. Educational content, not tax advice, rates and safe harbors have edge cases a professional should confirm for you.