PESEL is a number given to citizens in Poland (Polish acronym for „Universal Electronic System for Registration of the Population”). It starts with your date of birth and serves for common identification purposes. This number is very useful for managing certain formalities such as opening a bank account, registering for a doctor or submitting your annual tax declaration.
PESEL is automatically issued to you when you register your temporary residence at the municipality/district office (a procedure called in Polish meldunek czasowy). If it is not possible for you to register (for example the apartment owner does not give consent), you can apply for the number by yourself providing the below legal basis in the application form (stating that you require PESEL for tax settlement):
art. 3 ust. 1 pkt 1 ustawy o zasadach ewidencji i identyfikacji podatników i płatników (Dz. U. z 2020 r. poz. 170, z późn. zm.), w związku z art. 7 ust. 2 i w zakresie określonym w art. 9 ust. 4 ustawy o ewidencji ludności (Dz. U. z 2021 r. poz. 510)
The procedure of applying for PESEL is free-of-charge, however, the cost of issuing a paper confirmation certificate is PLN 17.