Other questions

Thank for getting back to this thread, DBETHEA.

Any sales transactions are only allowed to be linked in one customer. 

You'll want to use the copy feature instead, this allows you to copy the Invoice or any sales transactions you've made and link them to a different customer. 

Please see the screenshot below on where to find the Create a Copy in the transaction page. 

Please let me know if you have further questions. I'd be around to answer.