What can be done when a bill has not been paid on time?

You are automatically entitled to interest on arrears. Deferred interest is a legal requirement: you may not decline it and the administration is required to pay it. The amount due is a function of the number of days by which the deadline has been exceeded (automatically increased by two weeks). The rate of deferred interest is usually stated in the contract, and is equal to the official interest rate plus two percentage points.

When the rate is not stated in the contract, it is equal to the interest rate of the main refinancing facility used by the European Central Bank (ECB), plus 7 percentage points.