Offer letter is a document to have an MoU between employee and employer. There will not be any specific proforma or format for offer letter. A simple sentence reflecting the intention of the company to offer a such and such a job to the candidate, with a request to convey the acceptance of the candidate to take up the assignment, is enough. Based on the offer letter, the candidate may approach the company or firm, and negotiate with them regarding the terms of references of the appointment. Then, the appointment letter, mentioning the details of the salary and allowances ( CTC) as well as the terms of reference of the appointment, period of probation, extension, confirmation etc., will be given.