how did you respond to the letter? did you inform the IRS about the W-2 left off or was that contained in the letter? if so, now you know the problem. if the letter mentioned the W-2 or you included it the response the IRS will adjust the return accordingly. if you are still due a refund it could take 6 to 8 weeks maybe longer considering that the return must now be processed manually. if neither the letter nor the response mentioned the omitted W-2 you'll now have to wait for the refund and then file an amended return. it will still take 6 to 8 weeks. you can check the refund status at the IRS website.