Hi there, you are spot-on in your thinking all the way around ... but you will want to relate ClientID from the clients table (called a parent or primary key) to a ClientID in your Invoices table.
I just uploaded a very simple file which shows how to use names with their IDs and make that information easily available in another table. If you wish, you can read this link
In my last post, I include a link to the demo file. I believe this is exactly what you need here but if not, or if you get stuck, let us know.
Thank you LaRetta!!! This is EXACATLY what I needed. You've saved me a lot of headache :))))!!!!