How to checking for conditions before going to payment page on checkout page
I am making a webshop and i have some issue with add_filter.
When a customer is on a the checkoutpage, i want to check some condition when customer clicks on place order. Before it go’s to the payment page. And show some notice.
It must like the checkmark for Terms&Conditions. Before press the place order it need to check the condition.
What is the filter to check this? how can i achieve this?