Brazil thirteenth salary and taxation
The Brazilian 13th salary is not one extra month of pay handed over at once: it splits into two installments with different deduction rules, and the final net amount depends on how many twelfths the employee earned in the year, not the bare nominal salary alone.
The full 13th salary would be R$ 3,000; with only 6 of the 12 full twelfths in the year, the proportional value drops to exactly half, R$ 1,500.
This R$ 750 figure is gross and final: no deduction applies to the first installment, so what the employee receives here does not change afterward.
The R$ 113.82 INSS withholding is calculated over the full proportional value (R$ 1,500), not over the isolated R$ 750 second installment, but it is deducted entirely from that installment because the first already went out with no deduction.
One avo is earned per month with at least 15 days worked; each avo is worth 1/12 of the salary. Months with fewer than 15 days do not count.
Because the legislation governing the two-installment payment (Law 4,749/1965) concentrates INSS and income tax deductions into the final settlement, calculated over the full proportional value; the first installment works as a gross advance, and the tax adjustment happens only when the second installment is paid.
Working 15 days or more in the month is enough for that twelfth to count as a full month, a rule from Law 4,090/1962; someone who works fewer than 15 days in that month does not add that twelfth to the year total.
The 13th-salary withholding is calculated exclusively at source, separate from the employee monthly payroll; while it uses the same progressive table in force, the base is only the 13th-salary value (full proportional amount minus its own specific INSS), without adding it to the month salary for bracket purposes.
Yes, when they are habitual: the 13th-salary base adds the fixed salary to the averages of variable items paid regularly during the year, such as overtime and premiums, so someone who receives overtime frequently gets a larger 13th salary than the bare nominal salary alone would suggest.
⚠️ Educational estimate. Confirm with accountant or payroll professional.
Lei 4.090/1962 + Lei 4.749/1965; INSS sobre total do 13º (tributação separada); IRRF exclusivo na fonte; avos por ≥15 dias trabalhados/mês.