Cannot import quickbook desktop file to quickbooks online

It was my pleasure to assist you today, mark-sebs-proper. I can help you import your QuickBooks Desktop file to QuickBooks Online. 
 

There are two requirements you need to complete to be able to import the data to QBO.  

These are the following: 

• Make sure QuickBooks is up-to-date
• The company file isn't too big to export. The target should less than 500000. Simply press the Ctrl + 1 on your keyboard 

If you meet the requirements, we can verify and rebuild your data. It's possible that the file you're importing is corrupt. 

Verify your company data: 

1. Go to File, select Utilities, then tap Verify Data.
2. If QuickBooks reports a problem, continue to rebuild data. 

How to rebuild your company data to repair problems: 

1. Go to File, select Utilities, then choose Rebuild data.
2. If you see the message Rebuild has completed.

If issue persist, you can continue to other steps (3) in this article: How to resolve issues when importing from QuickBooks Desktop for Windows to QuickBooks Online. 

 I'm also adding these references that will guide you in converting your data and setting up your QBO company:

• Move your QuickBooks Desktop file to QuickBooks Online 
• Get more info about what data does and doesn't export from QuickBooks Online  
• Getting Started with QuickBooks Online

Should you have additional questions about importing or anything else QuickBooks-related, please let me know. Keep safe!