If the invoice number prefix in BUSY currently shows 00 which is causing issues,to mofigy the invoice number prefix correctly,follow these steps:
Step 1:Go to the Administration menu,
Step 2:Click on Configuration,
Step 3:Click voucher series configuration,
Step 4:Click on sales and select series,
Step 5:Click voucher numbering,here you can check what you are mention in prefix or padding characters,modify it according
to your requirement,save this configuration,
Step 6:Now you can go to the voucher and check it,issue will be resolve.