Earned Income Tax Credit (EITC) Calculator

The calculator models the EITC as a three-stage piecewise process: a phase-in (credit increases with earned income at a fixed rate up to a maximum), a plateau (where the credit is at the maximum), and a phase-out (credit reduces as income exceeds a threshold).

Basic disqualifiers are applied: investment income above the illustrative threshold, lack of valid Social Security numbers, nonresidency, and filing as married filing separately — any of these will result in an estimated credit of zero.

Results are computed deterministically from inputs. For traceability and auditability we surface intermediate values: maximum credit for family size, earned portion, and phase-out reduction.

This estimator provides an explainable estimate of EITC using piecewise arithmetic and clear intermediate values. It intentionally surfaces assumptions and intermediate calculations so users can validate and cross-check with official IRS tables.

For official filing, always use the IRS rules, tables, and publications for the exact tax year and consider professional tax assistance if your situation is complex.

Example: Single filer, one qualifying child, earned income $18,000, AGI $18,000 — earned portion is computed by phase_in_rate × income, then reduced by phaseout if income exceeds phase_out_start. The estimator reports the intermediate values alongside final estimate.

Example: Married filing jointly with two qualifying children, earned income $30,000 — the estimator applies the married filing threshold adjustment when computing the phase-out start.