I value your time posting here again to clarify some things, @CyberSpyder.

Though invoices and sales receipts are similar, their difference lies in issuance and utilization in your accounting. Not to worry, I'm willing to help you record the payment and link them to the invoices in QuickBooks Online.

An invoice payment link is a simple way to request a settlement from customers paying for goods and services. It automatically creates a Sales receipt as a record of a completed sale. That's why linking this to an invoice is unavailable.

Please know that deleting or voiding the sales receipt to avoid double posting will not automatically add the payment. Therefore, we need to receive payments manually on the invoices to mark them as paid.

Here's how:

1. Open the sales receipt.
2. Select More and choose Delete.

Once done, open the invoice and click the Receive payment button. From there, tick the invoice and deposits. You can follow these screenshots as your reference:

For more ways of receiving customer payments, refer to this article: Record invoice payments in QuickBooks Online. It will walk you through documenting partial payments and grouping them into a single deposit.

I'm adding this guide to learn how to personalize invoices and other sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If I can be of help while working with invoice payments, feel free to let me know by adding a comment below. I'd love to hear how it goes on your end. Have a great rest of your day.