The law that applies to the underlying transaction or occurrence.
In terms of section 11(d) of the Prescription Act, No. 68 of 1969, claims are extinguished by prescription three years after they arise. In terms of section 12(3) of the Act, prescription begins to run (i.e, a claim arises) from the date on which the creditor knows the identity of the debtor and of the facts from which the debt arose.
According to the principles of South African private international law, matters of procedure are governed by the domestic law of the country in which the relevant proceedings are instituted (lex fori). Matters of substantive law, however, are governed by the law that applies to the underlying transaction or occurrence (lex causae). In South African law, prescription is regarded as substantive.
Therefore, a South African court seized with the question of whether a claim to the enforcement of a foreign judgment has prescribed will apply the relevant foreign law.