Thanks for reaching out to us here in the Community, @fyarwood.

Please be assured that we strive to provide complete customer satisfaction at all times and to resolve any issues as quickly as possible. We'd appreciate it if you could please provide us with more specific information about your concern. This is to help us determine the best resolution appropriate for you.

You can leave a response, and we are available to help. Have a great day ahead.

My main question is will the clients old accountant backup override any new information I enter

We appreciate you for clarifying things about your concern with backing up company files in QuickBooks Online, @fyarwood.

I'd like to share some details on how it works.

Only the Advanced version currently has the ability to back up an existing QBO company. This replaces whatever information you entered and overrides the company data.

If you're presently using QBO Advanced, here's how you can do it:

1. Make a blank company file.
2. Set up the Online Back-up & Restore feature.
3. Reproduce a QBO Advanced company.

See this module for the complete steps: Make a copy of your QuickBooks Online Advanced company.

I'm also adding these guides about file management: Back up and restore your QuickBooks Online Advanced Company.

Please let us know if this goes. You can always leave a comment below so we can assist you with any data management or QuickBooks concerns. Stay safe!

@fyarwood 

Do nothing before you convert data. Otherwise, you may need a third party service to merge the converted data with the new transactions/information you enter.