A debt that cannot be recovered at law because its time limit has elapsed. The time limit within which action must be taken is set out in the Limitation Act 1939; it is six years for an ordinary debt or twelve years for a debt under seal, or a specialty debt. The time runs from the end of the credit period.
The time can begin to run again if the debtor acknowledges the debt. This may be by making a part payment or by acknowledging the debt in writing. The debt may also be revived if the debtor does anything which admits the continuing existence of the debt.
Reference: The Penguin Business Dictionary, 3rd edt.