If not, it should go in informing the host in advance to host will know the number of guests.In the work, but in General should be told before the day, whether or not.
If the job does not Let your host know in advance. The hosts will have to know the number of guests at the event. But in general, should be told the day before, whether it's possible or not.
If you go in the job, should let the host know in advance. To the host to guest source phrases recognition in the job. But, in general, should say the job, whether go or not.