Invoice is related to the time of payment, but not to the time of publication. Whether it is the core or the general problem, tickets can often be issued after payment, sometimes once a month, and sometimes at any time. Of course, it is not surprising that some of them are not given at all. Generally, the payment is made when the employment is confirmed, so the invoice is also issued at that time, and there is still a period of time before it is officially published.