Whats the best practice for changing the Customer on a Sales Order thats been billed? ie Sales Order gets entered under Customer A, gets shipped on an Item Fulfillment under Customer A, gets billed on an Invoice under Customer A. Then we realize the customer is wrong, and need to move the Sales Order, Item Fulfillment(s) and Invoice to Customer B. How should that be handled?

I haven't had a clean way to fix this, but at go live we a lot of these problems - especially when the orders had multiple IF's. I made a Suitescript that would update the customer from Invoice, downstream. Be careful though that all reliant information fills in on those records as well.

You also run the risk of breaking related transactions from the original sales order if you try and change directly in transactions. Best practice unfortunately is to delete backwards (invoice, then Item fulfillmen) change the sales order, and run back through creating new IFs and Invoices.

As @Michael McNamara said, that's definitely the cleanest way, just sadly is a pain

Major pain! But that’s the process.

Thanks all. I thought that was the answer, but I was hoping for an easier way. Oh well!

you could RMA and credit off the invoice and then recreate the SO, IF and Inv. That would be a cleaner way to show what happened in the system.