Hey there, @ben62. If you'd like to move an Invoice and associated payment,  make sure you also switch the name on the Payment to the project, as outlined in reginamarie's above. If both the payment and invoice names don't match and you try to link the two, it can throw off balances for each, since they're separate A/R accounts.

My colleague's above have also provided some great resources that I recommend checking out.

Let me know if you have any other questions by using the Reply button below. I'll be here to help out. Have a good Wednesday.