Thank you for posting, @Jan H - WY.
You'll just have to create an invoice for this transaction and then receive the payment.
To create an invoice:
Then, record the payment twice. One from March and the other is on April 2019.
To record a payment toward an invoice:
You can perform the same steps to record the payment received on April.
From here, those amounts will now appear on March and April 2019 to reconcile those transactions.
Check these articles for more information on how create the invoice and receive the payment: Accounts Receivable workflows in QuickBooks Desktop.
Here's an article on how to fix issues when you're reconciling in QuickBooks Desktop.
Let me know if there's anything that I can help in reconciling your account. I'm always glad to help in any way I can.