Spain-TaxSim
IRPF simulator handling Spanish tax bands, deductions, and the regional variations that catch everyone off-guard.
Private build for myself and a few friends — no public repo or demo.
Python
Spanish tax computation, taken seriously. The Spanish IRPF system has progressive bands, a state-vs-regional split, deductions that vary by autonomous community, and special rules for things like investment income and rentals — exactly the kind of branching rule-set where calculators quietly go wrong. The goal here was to encode all of it and make every assumption explicit rather than buried.
I built it for myself and a few friends; it’s a useful exercise in turning a regulation document into a deterministic program — and in respecting how much correctness work hides in the edge cases.