1099 quarterly estimated taxes — the 4 dates

The four dates

The dates come from IRC §6654 and IRS Form 1040-ES. Note the shape: the periods are not calendar quarters — the second covers two months of income, the third three, the fourth four.

Why quarterly at all

An employee's taxes are withheld from every paycheck. A self-employed worker has no withholding: the year's self-employment tax, federal income tax and state income tax are prepaid in these four installments instead, and settled on the annual return.

How the estimator on this site splits the year

Four equal installments of the estimated annual total — the method documented in the engine's parameter file. Pick your state and income in the quarterly estimated tax calculator and each payment is computed from the same full-year result as the 1099 pages. Each installment is rounded to the cent separately, so the four payments can add up to a few cents more or less than the estimated annual total — that is how estimated payments work in practice: each installment is computed and paid for its own period.

Safe harbors: real, but not modeled here

Real Form 1040-ES planning can lean on safe harbors — paying at least 90% of the current-year tax, or 100% of the prior-year tax (110% for higher incomes) — and on the annualized-income installment method when income arrives unevenly. None of that is modeled in this engine, and underpayment penalties are not computed: the equal-installment figure is the planning baseline, not a guarantee against penalties.

What to do with the number

• Quarterly estimated tax calculator
• Self-employment tax calculator
• Methodology: the self-employment engine