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:

1. Go to the Customers menu and select Create Invoices.
2. Click the Customer:Job drop-down arrow to select the customer from the list.
3. Make sure to set the correct date from last year. 
4. Add all the necessary information. 
5. Click Save & Close once you’re done.

Then, record the payment twice. One from March and the other is on April 2019. 

To record a payment toward an invoice:

1. Go back to Customers menu and then Receive Payments.
2. Click the Received From drop-down arrow and select the customer.
3. Set the date of the first payment and enter the payment received on March 29 under the Payment column.
4. Choose the bank account into which to deposit this payment.
5. Click Save and close once you’re done. 

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.