I am posting older invoices and need to enter the payment. I want the date to reflect the actual payment not today's date. Is there a way to do that?

Hello there, different74.

The option to edit the invoice actuals' payment isn't available in QuickBooks Self-Employed but, there's nothing to worry about it.

The system will consider as to when the transactions are categorized.

In case you'll be collecting sales tax, you can check this article: Collect Sales Tax.

I'm just around if you still need my help. Keep safe!