this was the module I was using and is causing the problem https://addons.prestashop.com/en/other-payment-methods/2260-oleapaydiff-deferred-payments-to-end-of-month.html
Just like to add this module has served me well it was a great solution at the time but due to the way my business now operates I no longer require it otherwise it would still be in use, we just don't offer credit anymore 