Model Germany's § 1a KStG corporate-tax option for partnerships in a focused advisory workflow. Compare the transparent default model, the corporation-tax option, and a GmbH conversion path using profit, municipal trade-tax multiplier, distribution rate, partner shares, additional taxable income, church-tax status, and assessment type. The app models corporate income tax, solidarity surcharge, trade tax, withholding tax on distributions, and the § 35 EStG trade-tax credit in the default partnership model. Multi-year projection, sensitivity analysis, quick-pick municipal multipliers, and the filing-deadline tracker help prepare a better client conversation. Premium Pro unlocks scenarios beyond three years, more than two partners, the full GmbH comparison, PDF/CSV export, and ad-free use. This app is not tax advice under German law. It is a calculator and comparison tool; binding decisions should be reviewed by a qualified German tax professional.