How does the annualized income installment method work for 2026?
It measures each instalment against the income you had actually earned by that point in the year. For tax year 2026 the four periods end March 31, 2026 through December 31, 2026; income in each is multiplied by that period’s annualisation figure — 4 for the first — and the tax on the result is taken at 22.5% for the first instalment, rising to 90% for the fourth. Even the social security ceiling is prorated, from $46,125 to $184,500.
United States · federal · tax year 2026 · every figure from an open dataset with its source
The figures
| Period ends | Annualisation multiplier | Applicable percentage | Prorated social security limit | Half-of-SE-tax divisor |
|---|---|---|---|---|
| March 31, 2026 | ×4 | 22.5% | $46,125 | ÷8 |
| May 31, 2026 | ×2.4 | 45% | $76,875 | ÷4.8 |
| August 31, 2026 | ×1.5 | 67.5% | $123,000 | ÷3 |
| December 31, 2026 | ×1 | 90% | $184,500 | ÷2 |
This is the method for income that arrives unevenly. Someone who earns almost nothing until the autumn owes very little by the June date under this method and a great deal under the ordinary equal-instalments rule, and only this method will show it. The price is that every period has to be computed separately, with different figures each time.
The table is the one restated for 2026 by Pub. 505 Worksheet 2-9, which feeds Schedule AI of Form 2210. Nothing here decides whether the method is worth using: it usually helps only where income is genuinely lumpy, and it needs records good enough to say what had been earned by each of those four dates.
Where these figures come from
Each row below is one line of our open dataset: the primary document the figure was read out of, the date it was read, and a link to the document itself. Nothing here was copied from a summary of a summary.
| constant | basis | source document | verified on |
|---|---|---|---|
ai_period_end_dates |
structural | IRS Publication 505 (2026), Tax Withholding and Estimated Tax, Worksheet 2-9 column headings | ✓ verified |
ai_annualisation_multipliers |
structural | IRS Publication 505 (2026), Tax Withholding and Estimated Tax, Worksheet 2-9 lines 2 and 5 | ✓ verified |
ai_applicable_percentages |
structural | IRS Publication 505 (2026), Tax Withholding and Estimated Tax, Worksheet 2-9 line 22 | ✓ verified |
ai_prorated_ss_limits_2026 |
indexed | IRS Publication 505 (2026), Tax Withholding and Estimated Tax, Worksheet 2-9 line 34 | ✓ verified |
ai_half_se_divisor |
structural | IRS Publication 505 (2026), Tax Withholding and Estimated Tax, Worksheet 2-9 lines 42-43 | ✓ verified |
Work out your own
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The whole dataset
Every figure on this page, and everything around it, as a table you can read and as CSV and JSON you can download. Public domain, no attribution required.
Nearby answers
This is a reference table, not tax advice. Verify any figure against the linked primary document before relying on it.
