A US Person has an existing interest bearing checking account with us. We file form 1099-INT on his accounts each year.

Today he adds an NRA to the account. We know interest will still be reported using form 1099-INT and the US Person's TIN.

Would you get a W-8BEN certification from the new account owner even though her foreign status will not affect the way we report interest? I have read through some of the older threads and the webinar materials from last year, but I am still not sure if this would be advisable since the W-9 for the primary owner rules for tax reporting purposes.

We do not. Our stance is why get it when you don't need it and worry about getting the W-8 BEN's updated etc. If they become primary on an account we get it then. The only time you would need a W-8 for all is if they are all non-resident aliens (without green cards).