ACCA in general gives you a timeline of 30 days to make the payment once the Invoice is raised, in case the student tends to make part payment due to financial issues you can do a part payment but you have to ensure you complete remainder of the payment in a stipulated time. Delayed payments may cause removal of name from the register.

For detailed guidelines on part payment – you can visit the link below
https://www.accaglobal.com/content/dam/ACCA_Global/Students/email/paymentoptions.pdf