Currently if you offer an early payment discount, when AccountRight processes the payment it uses a sales invoice number rather than a Sales Journal number (per attached screenshot).
In this case; Sales Inv 15 should be some other number series as you don't want normal invoice numbering to be affected.
When the client has pre printed order books, using the sales invoice numbers causes issues as the staff on the front desk can't find out which invoice number is next.
"Don't use sales journal invoice numbers for credits due to early payment discount"