In my experience HR can take any time from a week up to a month to respond with a letter and formal offer or acceptance. I also want to provide the proper 2 week notice period, and I would like my manager to hear from me and not HR. So, when do I tell my manager?What is A Offer Letter? An offer letter is a written document that an employer sends to a job candidate to formally offer them a job. Deadlines (All deadlines are at p.m. Do not give notice until they've formally offered the new position in writing and you've formally accepted in writing. Do not give notice today. Accept the job formally: Start the letter or email with a formal declaration that you accept the job offer. To avoid confusion, you can confirm your notice period and start date in your acceptance email.