Hello e.ramirez,
Thank you for posting here in the Community. I want to help you with your concern about adding an Excel report in QuickBooks Online.
If you're referring to adding Excel reports as attachments, you should be able to do it directly through your email provider. Most Email Services allows you to attach files and pictures with file size limits.
If what you meant are your schedule reports within the QuickBooks system, you have the option to attach them as an Excel file. For your visual reference, I'm adding a screenshot I recommend on this:
Please let me know if you need further assistance on this. Any additional clarification like a screenshot or further details will ensure a timely solution.