The FSB, South Africa's financial regulator, said on Tuesday it had done this to limit new investors' exposure to the lender's bad debts.
Earlier this month, the bank commonly known as Abil received a 1.6 billion US dollar bailout by South Africa's central bank as bad debts soared among its core market of low-income borrowers.
The FSB said the move would impact collective investment schemes, which pool investors' money in funds run by professional managers.
"The move seeks to assist managers to segregate the less liquid Abil assets within their portfolios from the remaining assets and in so doing limit new investors into the fund from exposure to the [DATA ABL:African Bank Investments Limited] debt," the FSB said in a statement.
The FSB said should collective investment schemes choose to create the "side-pocket" funds, existing unit holders would have units in two funds, the original and the secondary fund.
The FSB said it had received applications for side pocket portfolios for 50 funds exposed to Abil at the close of business on 18 August.
Abil ran into trouble after years of aggressively pushing high-margin loans that are not backed by collateral to low-income earners. But high levels of household debt, unemployment and rising inflation have pressured borrowers into defaulting.