Co-borrower (współkredytobiorca)
A person who takes out the loan together with you and is liable for repaying it in full, not just their share. Most often a spouse, partner or family member.
When assessing creditworthiness, the bank adds up the income of all borrowers, but also counts their expenses and commitments. Liability is joint and several: the bank may demand the whole instalment from each of you. Being a co-borrower does not automatically make anyone a co-owner of the flat — ownership is decided by the notarial deed.