Keep the original event
A posted receipt is part of the school’s financial history. Corrections should record what changed, why it changed and who approved it.
Re-point the allocation
If money was applied to the wrong fee type, move the allocation while preserving the original payment amount and reference.
Close the loop
The corrected receipt and statement should make the change visible to staff and the fee-paying guardian.
The useful test
Could a newly appointed member of staff follow this process without relying on somebody’s memory? If not, make the rule visible before digitising it.