Apple has banned the practice of bonded labour, where new recruits are charged a fee before they start working.
In its latest audit of factory conditions, the iPhone maker said that any recruitment fee must be paid by the supplier and not the employee.
Apple began the audits following criticism of the working conditions in some of its factories.
It comes as a report from labour rights group China Labor Watch questioned the low wages earned by some Apple workers.
Its 2015 Supplier Responsibility Progress report said it had told its suppliers in October that it was outlawing bonded servitude from this year.
“That fee needs to be paid by the supplier, and Apple ultimately bears that fee when we pay the supplier, and we’re OK doing that,” said Jeff Williams, Apple’s senior vice-president of operations.