You can also use the more formal "Serdeczne gratulacje" (pronounced "ser-DET-sh-neh grat-oo-LAH-tsee-eh") which means "Sincere congratulations."
You can also use the more formal "Serdeczne gratulacje" (pronounced "ser-DET-sh-neh grat-oo-LAH-tsee-eh") which means "Sincere congratulations."