Hi there, C2 RV. 

I understand that you changed the amount on the invoice to $200. However, you can revert it to its original amount. With QuickBooks Payments, you can refund a customer who paid you with a credit card directly from the invoice.

Here's how:

1. Go to the Sales tab, then select All sales.
2. Find and select the sales receipt, invoice, or payment you want to apply for a refund.
3. In the footer, select More, then select Refund.
4. Review the transaction info, then select Save and close.

Please know that if you need to issue a partial refund, you can edit the item or amount accordingly.

Also, to set an expectation there will be a fee once you process a refund. You can visit our article to see the pricing plan.

I'll leave this article for you to follow the detailed steps on how to void or refund customer payments in QuickBooks Online.

In addition, you can check this article if you want to learn how to record payments in QuickBooks Online: Record invoice payments in QuickBooks Online

Don't hesitate to leave a comment if you have other concerns with processing a refund or managing your invoice. The Community is always here to help. Take care.