Viva La Tax is a free, open-source tax filing engine that lets you see exactly how every number on your return was calculated. Upload your W-2s, 1099s, and K-1s (or enter your info step by step), and the engine computes your federal and state returns with full line-by-line transparency. Download completed IRS forms as fillable PDFs. - Federal Form 1040 + all major schedules and forms - 15,000+ automated tests against IRS instructions - Self-host with Docker