In the hospitality field, there are many companies running branded chain of restaurant, but they do not issue any appointment letter nor offer letter. Here the Management's thought process is that if a person needs a job and we have a vacancy for which we find him suitable, he should be asked to join.
The Tacit understanding being that the person will be on probation for 6 months and will thereafter continue to work for the organisation as long as he keeps getting his salary on time each month.
Its a matter of trust. However in case of an employee leaving the Company after say 1 year or more he is provided a service certificate mentioning his date of Joining , Designation, period of Service and his last drawn salary.
If is is a large group and internal email is sent to all concerned informing that the person has joined, and the same is put on record.