When the guest says that there is no invoice we can refuse to pay. What should the restaurant do

At that time, it was not possible to use it. Generally speaking, customers ask for invoices mainly to be reimbursed, or they want to win the lottery. And if you pay for your own meal, you generally won't ask for an invoice.

Therefore, most customers will not take the initiative to ask for invoices. Then the restaurant will not take the initiative to give an invoice in order to pay less tax.

For the customer, he doesn't care where your invoice comes from, he only cares about whether the invoice you give him can be reimbursed. So when the restaurant says that it has been used, as long as it can be reimbursed, the customer will accept it.

But in reality, this is not legal.

It is not legally used by reason, but some customers are acceptable. In addition, you can give the guest a little discount, just according to the number of points on the invoice. It's also a tax saving, right? It's not an ethical thing though.