How do I raise a credit memo to match an invoice with multi period accounting

When a tuition fee bill is raised in Oracle, multi period accounting is applied, so that the system automatically recognises the income over the duration of the course length. For example, a course or programme starting in September running for 11 months, the system will recognise 1/11 of income in each month from Sept to July the following year.
It was understood that any credit notes raised would work on the same principles and that the credit note would apply the same multi period accounting rules as the original bill that it related to. However, this doesn't seem to be happening. The full amount of the credit note is getting recognised in full in the month that it is raised, rather than splitting it over the course length. This is causing various problems when it comes to financial reporting and reconciliations.