What's the actual difference between umowa o pracę and B2B in Poland?
Umowa o pracę (UoP) is standard payroll employment under the Kodeks pracy: your employer withholds PIT and your employee-side ZUS/NFZ, and separately pays employer-side ZUS (about 20.48% of your gross) on top of your salary as a real cost that never appears on your payslip. B2B (jednoosobowa działalność gospodarcza) means you invoice as a sole proprietor and choose your own taxation mode (skala, liniowy, or ryczałt), paying your own ZUS and NFZ directly. UoP includes paid leave, sick pay, and severance protections; B2B typically doesn't, but usually nets more at the same headline figure.