I am using version 4.48 for a small sports club. I wanted to amend the invoice number to end with a letter of the alphabet so at a glance the members could see from the invoice number what it relates to. E.g 10001M relates to membership, 10002F Fees etc. The only way I could do this was to use the prefix and have M10001, F10002. This is fine except the invoices list alphabetical order instead of numerical. It wont allow letters in the number field. Is there a way?