Hello there, @DaytoDay.
If checkmarks are missing in the Bank Register or Reconciliation window in QuickBooks Online (QBO), there could be several reasons for this issue. Let me guide you through the troubleshooting steps to help resolve it.
One of the possible reasons you are unable to see the tick box in Bank Register or the Reconciliation window is that the Reconcile and Banking Status column is hidden. You can add the column by following the steps below:
- Open the correct Bank Register you want to work on by clicking its Account history.
- Click the small Gear icon inside the page.
- Tick the checkbox for Reconcile and Banking Status.

You should now be able to see the tick or checkbox column for the reconciliation status. It will display either a blank space, 'C' for cleared, or 'R' for reconciled transactions in QuickBooks Online.
If you have any additional questions or encounter any issues while managing bank transactions in your QuickBooks Online account, feel free to share them in the comments below. We're here to help.