In terms of the Prescription Act, 68 of 1969, most debts are prescribed after 3 years. Some type of debts have their periods for prescription. Prescription can be interrupted in several ways. One of these is if you have made a payment on the debt, then the prescription will start to run from the last payment date.
Judgement debt, for example, prescribes after 30 years and to have this reversed the said debt must be paid in full. Credit bureaus list judgements on your credit profile hence the old terminology being referred to as ‘blacklisting’.