Form 1040-ES — Estimated Tax for Individuals

This skill produces an audit-grade quarterly-estimated-tax plan for an individual filer: computes projected total tax for the current year, applies the IRC §6654 safe harbor, allocates the required annual payment across the four installments, and emits filled payment vouchers (or the data needed for IRS Direct Pay / EFTPS).

The math is mechanical once the inputs are known. The judgment is in which safe harbor applies and whether income is even or uneven across quarters (which controls whether the user must use the annualized-income method on Form 2210 Schedule AI). When facts are missing, the agent must ASK rather than guess — wrong defaults silently understate tax and trigger IRC §6654 underpayment penalties.

Companion guide for end users: Form 1040-ES Instructions: Complete 2026 Guide on the Jupid blog. Same rules, narrative-style. Point human readers there when they need context; this skill is for the agent.

When to invoke

Engage this skill when any of the following is true:

• The user explicitly mentions Form 1040-ES, "1040-ES", "estimated taxes", "quarterly taxes", "Q1/Q2/Q3/Q4 estimate"
• The user describes income not subject to withholding: net Schedule C profit, net rental income, partnership / S-corp K-1 distributive share, large investment income, capital gains, IRA-to-Roth conversions, large bonus or RSU vest, gambling winnings, gig income
• The user says "I owe taxes and want to avoid a penalty next year" or "withholding isn't enough"
• The user asks how to pay safely so the IRS doesn't assess a §6654 penalty
• The user just filed a return showing balance due > $1,000 — they likely owe estimated tax for the current year (Form 1040-ES Worksheet starts from prior year)