Today I got a very nice tip from a colleague on how to better understand and see the source code for the retail components. I was experiencing that I was not able to post a CPOS sales, and in the eventlog I got the following “Cryptical” error: Customer with RECID 5637158076 is non-chargeable account. at Microsoft.Dynamics.Commerce.Runtime.Services.CustomerPaymentService.ValidateCustomerForOnAccountPayment(Customer customerToPayWith, RequestContext context, Boolean isPositiveAmount) The thing with the retail server, is that we don’t have the source code on all the components. But luckily there are a way around it: JetBrains dotPeek (just google it, and download) This tool let you decompile all components, and have an advanced search capability. Just all the K:\RetailServer\WebRoot\bin\Microsoft.Dynamics * files, and then search for the term ValidateCustomerForOnAccountPayment: Solution to my problem, was that the InvoiceAccount on the customer record was blank. So now you know how to see all sourcecode in Dynamics 365 Commerce/RetailServer components Happy!