Since 2023, an autónomo doesn't choose their own Social Security contribution base the way they once could. The RETA system now ties your monthly cuota directly to your estimated net income, rendimiento neto, revenue minus deductible costs minus an additional 7% flat deduction, divided by 12 and matched against one of 15 tramos.
That cuota isn't a separate cost sitting outside your tax calculation, it's a deductible business expense in its own right. This calculator applies it exactly that way: the annual cuota comes off your net income first, and only what remains is subject to IRPF, the same progressive scale any Spanish taxpayer faces.
New autónomos get a real break at the start. The tarifa plana lets first-time registrants (or anyone who hasn't been registered in the prior two years) pay a flat, low monthly amount for their first year, regardless of which tramo their real income would otherwise place them in, extendable to two years if income stays below the SMI. This calculator focuses on the standard ongoing cuota instead, since it's built for comparing steady-state income once that introductory period ends.
What isn't automatic is your final tax settlement. Autónomos file estimated quarterly IRPF payments (Modelo 130) through the year, then true everything up in the following year's Renta return (Modelo 100). The final net figure this calculator shows is that eventual settled annual number, not a quarter-by-quarter cash-flow schedule.
