I have been talking to one of the Big 4 for the last few months and was verbally offered a role after 3 rounds of interviews - the final round was with the partner of the practice.Its been 3 weeks since the verbal offer, but I have not not received any formal offer letter from them.Can you provide any inputs on typically how long do they take to send the offer letter? Also, is it because of the time of the year, being holiday time and all, that the offer letter is being delayed?