Please can you tell me how I credit note a client for a higher value than the original invoice?
My client paid £225.00, there was a problem so we are giving them £345.00 back but when I try and either credit the invoice it wont let me because the value is higher and if i try and raise a new invoice with a negative balance it says it must be greater than £0.00.
You should be able to create a new invoice with a negative balance. Where did you see the error about the value?
What you would need in this case, is either raise the higher value credit note (but this will require a bank transaction), or credit the invoice and add a prepayment for the diference to their account as a “goodwill gesture”. There’s a guide on recording this here which may help.