I have a problem with the exact English legal expression of the situation when the debtor is obliged to pay a certain sum of money at the stipulated time and he fails to do so (he does not pay duly and on time). I usually translate it as "the debtor is in default" but recently I have found the expression "the debtor is in delay with payment". Which one is right... I have a strange feeling that none of them Emotion: stick out tongue
You may be looking for the word "delinquent." Your account is delinquent. You are ten days past due on your payment.

In the strictest sense, as soon as the debtor violates the agreement (which includes paying on time) you can say he is in default. Often, however, you reserve "default" to be a very serious delinquency and the account will be closed or other significant action is pending.

In the U.S., government student loan terms are a little different.
Generally, if a debtor has not made payment and fails to rectify the situation within the time stipulated in the contractual undertaking, the debtor is said to be "in default". The other translation might be correct but without more detail and context it is difficult to say. I think it probably safe to stay with "in default".