attaching a file

Thanks for posting here in the Community, @SLOOP. I'd be happy to help you attach a bank statement in the completed bank reconciliation in QuickBooks Online (QBO). 

The option to attach bank statements in completed or pause reconciliation in QBO is only available for the Plus, Advanced, Accountant, and QuickBooks Live versions. However, your bank should be connected to the online bank feed, to automatically get bank statements. 

To do so, simply select the Attach statement button after completing the reconciliation. Please see the screenshot for reference:

For reference, check out this article: Get bank statements directly from your bank when you reconcile. 

To have an additional guide in performing the reconciliation process, please read this link: Learn the reconciliation workflow in QuickBooks. 

Once the reconciliation is finished, the program automatically creates a reconciliation report for that session. To pull up one for the previous period, check out the steps in this article: How do I view, print, or export a reconciliation report?

If you have any other concerns about managing reconciliation in QBO, please don't hesitate to leave a reply below. I'd be happy to provide additional assistance. Have a good day ahead and stay safe.