How do I revert a paid invoice to unpaid?

I marked an invoice as paid when I was triying to mark as sent.

I deleted the payment in the right column of the invoice (Payments).

But in the right column of the invoice (History) appears the payment record.

Thanks in advance for your help.

It shouldn't be deleted from history. What's the new status after deleting payment?

Hi Ahmet,

Appears as Sent because I marked as sent after marked as paid.

Here a screen of the bill.

https://ibb.co/h58TP6

So that's not a problem as Sent is an unpaid invoice.