Why do some terms keep their Polish form in translations?

Because the term is a specific Polish legal/administrative concept with no exact equivalent (e.g. zameldowanie). Keep the Polish word and add a short explanation, as in the locked glossary at content/_glossary.json.

Polish–English Glossary of Bureaucratic Terms

The Polish words you will see on every form as an immigrant — translated and explained, so forms stop being a wall of Polish.

This glossary explains terms you will meet on Polish forms. For locked per-locale translations, see the translator glossary (content/_glossary.json), which translators must use verbatim.

Identity and registration

PESEL — national identification number (11 digits).
zameldowanie — registration of your address at the municipal office.
karta pobytu — residence card (temporary or permanent).
dowód osobisty — national ID card (Polish citizens).
Profil Zaufany — free online identity for logging into government services.

Health and insurance

NFZ — National Health Fund (public health insurance).
ZUS — Social Insurance Institution (pensions, sickness, maternity).
SKN / ubezpieczenie zdrowotne — health insurance contribution.

Tax and business

NIP — tax identification number.
REGON — statistical business identifier.
PIT — personal income tax return (filed annually by 30 April).
JDG — one-person business / sole proprietorship (jednoosobowa działalność gospodarcza).
sp. z o.o. — limited liability company (spółka z ograniczoną odpowiedzialnością).
Ryczałt — flat-rate tax on revenue (an alternative to scale tax).

Offices

urząd gminy / urząd miasta — municipal / city office.
urząd wojewódzki — provincial office (handles residence permits).
Starostwo Powiatowe — county office (driving licences, vehicles).
UDSC — Office for Foreigners (Urząd ds. Cudzoziemców).
SOR — hospital emergency department (Szpitalny Oddział Ratunkowy).

Documents

akt urodzenia — birth certificate.
akt małżeństwa — marriage certificate.
tłumacz przysięgły — sworn translator (required for official translations).