I have tried for a long time now to make a AIM XML createTransactionRequest that at the same time creates a CIM profile based on the transaction. It constantly told me that <payment> was not allowed within <transactionRequest> ! Suddenly I realize that I get different errors depending on the order of elements within <transactionRequest>. The documentation doesn't talk anything about a required order of elements, but when I read the XSD closer I suddenly realize the sequence requirement! Not only does the documentation not mention that the sequence is important, it even lists <profile> and <payment> in the wrong order. <payment>  must come before <profile>.

I hope this can save someone from wasting a lot of time - and Authorize.net will correct and improve their documentation.

The documentation is also very fuzzy about the XML structure - what elements need to be created where and how they should be nested. You figure it out eventually but it could be A LOT clearer.

Oh how I wish we could soon get rid of XML and use JSON instead - it is so much better and simpler to deal with. We simply don't need all the complexity XML has.