Agregação Familiar — Joint Filing

Agregação familiar (family aggregation) is the option for married couples or civil partners (unidos de facto) to file a joint IRS return. Under joint filing, the couple's combined income is divided by the household divisor (quotient conjugal) — 2 for a couple — to compute tax, which is then multiplied back by 2. This income-splitting approach is beneficial when one spouse earns significantly more than the other, as it reduces the average marginal rate. Joint filing also doubles the standard deductions and credits. A couple may only file jointly; they cannot selectively combine or separate certain income types. The decision to file jointly vs. separately should be modeled annually — the taxpert.app calculator supports both scenarios.