I have found an answer to my question. In order to have Next Bill button available on the Sales Order, you just need to have 2 conditions met : There is still $amount to left to pay There is still items quantity left to invoice So in case, you, like me, have a single Engineering Services item on the sales order, and you…

I am still waiting on advise from our Account Manager, I he doesn't help out, I'll reach back to you (as you told me to do)