Dear Vamn,
Hence, your question is quite out of track. But if a person is interviewed by the organization and he gets selected for a particular function in the said organization, and he is also ready to join the organization, he will have to resign or be relieved from his previous or existing organization to pursue the new opportunity. If an offer letter is not issued to him/her, how will he/she assume that he has an opportunity to join the other organization? On what basis will he/she submit his/her resignation to his existing organization? Can a new employee be expected to join the organization without any written confirmation?
Suppose you assume the new employee will join the organization without a formal offer letter, or if they trust your verbal agreement to join on a certain date by submitting their resignation to their current employer. What if they show up to join your organization, having resigned from their current job, and you or your colleague deny having made any verbal agreement? Then what?
Altogether, we can say that an offer letter serves as an invitation for a new employee to join the new company/organization.
tnx
uc