I recognize your desire to convert Sales Receipts into invoice payments, Cyber. Let me provide more details on sending a payment link in QuickBooks Online and offer guidance on the most appropriate steps.

The feature for customers to make payments using the link and get credit on their account is only available in QuickBooks Desktop. In QBO, when you send a payment link to your customer, QuickBooks automatically generates a sales receipt if it's not the one from the invoice. The proper way to keep track of invoice payments in QBO is by using the Receive Payment functionality.

I recommend deleting the sales receipt and manually making payments to the invoice. Let me show you how:

To erase the sales receipt:

1. Go to the Sales menu then All sales.
2. Locate and open the Sales receipt.
3. Click on the drop-down icon.
4. Select Delete.                    
5. Then click on Delete to confirm.

To receive payment:

1. Click on + New.
2. Select Receive payment.
3. In the Customer dropdown, pick the name of the customer.
4. Go to the Payment method dropdown, and select the payment method (credit card, debit, PayPal, Venmo, or ACH bank transfer).
5. From the Deposit to dropdown, choose the account you put the payment into.
6. Navigate to the Outstanding Transactions section, and tick the checkbox for the invoices you're recording the payment for.
7. Enter the Reference no. and Memo if needed.
8. Click on Save and close. See the image below for reference:

Here's an article you can browse to learn more about how to record partial and/or multiple payments in QBO: Record invoice payments in QuickBooks Online. Kindly review the third and the last section for the detailed steps.

Furthermore, check this out in case you want to personalize your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Get back to this thread if you have additional questions about the process of how sales receipts and invoices work. I'll be around to back you up also about any QuickBooks-related concerns. Have a good one!