Amount of money paid periodically by the debtor to his creditor as remuneration for a loan or an unpaid sum of money. This sum is calculated on the basis of an interest rate expressed as a percentage and fixed by agreement between the parties. The interest rate must be indicated on an annual basis. The declaration of co-ownership (by-laws of the immovable) generally provides for an interest rate applicable to unpaid common expenses. If the latter is silent on this subject, the applicable interest rate will be the legal rate (article 4 of the Interest Act).