Bill Payment entered in March 21 and paid in April 21 does not show in creditors report for end of March?

Thanks for sharing a few details about your concern, @hobinlorraine@gm.

When running the Accounts Payable Aging Detail and Accounts Payable Aging Summary report, it'll show all your unpaid bills. Thus, if on the period range set on the report, you still have a balance on the Bill. Then, the bill will show. This is the reason bill payment won't show in the creditor's report.

But if you set the period range to the date after the post-dated check, then the system will recognize the payment in which the bill will no longer show on the report. 

You can take a look at this article for additional information: Run reports in QuickBooks Online.

Alternatively, you can run your Accounts Payable register to show all the related transactions under this account. To run, here's how:

1. In the left menu, click Accounting.
2. Go to the Chart of Accounts tab. 
3. In the search field, type in Accounts Payable.
4. Under the Action column, hit the View register link.

In addition, you'll want to see the bills and the payments applied, I suggest running the Bills and Applied Payments report. You can see this in the Reports menu under the Standard tab, then go to the What you owe section.

Feel free to post a comment if you have additional questions about running reports in QuickBooks Online. I'm always here to lend a hand. Take care!