Overdue status begins the day after the payment due date. In addition to the principal debt and interest, a penalty is charged, with its amount and calculation method determined by the contract.
Consequences escalate with duration. Initially, there are additional charges and entries in the credit history, then demand for early repayment of the full amount, enforcement against collateral, and debt collection proceedings. Each stage increases the total amount.
For credit history, both the size and frequency matter: several small overdue payments are assessed no less severely than one large one. Debt on a credit card or unused overdraft in a small amount can damage history just as much.
Practical rule: contact the bank before the overdue period begins, not after. Restructuring or schedule changes are available to borrowers who have not yet violated obligations, and terms are usually better in this case. Lenders with simplified borrower assessment charge penalties that grow especially quickly upon overdue.