Hello @ceceabel,

Thank you for dropping by here in the Community. I'm here to help you fix the check numbering in QuickBooks Online.

The check number sequence will depend on the last check entered into the account. To reset the order to whatever number you need, I recommend enabling the Customer transaction numbers from your settings.

It allows you to correct the numbering when creating a new check. The system will increment the number by one each time you enter a check transaction and generally follow the order.

Here's how:

1. Click the Gear icon in the upper-right corner.
2. Select Account and settings under Your Company.
3. Go to Sales.
4. Enable Custom transaction numbers under Sales form content. 
5. Hit Save, then click Done.

If you need to correct your existing checks, you'll need to make the changes manually. You can go to your chart of accounts to update the transactions.

Please follow these steps:

1. Click the Gear icon in the upper-right corner.
2. Select Chart of accounts.
3. Search the account.
4. Press View register.
5. Edit check numbers.

For additional reference, I've attached a link you can use to run a report with checks sorted by number, as well as how to export data to Excel: Print a report in check number order.

Click the Reply button if you need assistance with the check numbering in QuickBooks. Have a great day ahead.