How to sell sold out products?

Everyday life shows that stock levels are not always correct. It must therefore be possible to sell a product in the checkout even if there is no stock.
In this case, a message must appear and the cashier must be able to bypass the stock or actively confirm the sale. In this case, the stock level should be increased by the number of units sold and then the product should be sold so that the same stock level is available after the sale as before the sale.
How can this be achieved?