You have 30 days from the date of a 30-day letter to respond, as the name implies. Whether you choose to accept or appeal, the notification will clearly clarify the options open to you at this time. If for some reason you believe that you have been incorrectly classified, then you can file an appeal. It is important to respond to these letters because if you fail to do so, your employer may begin withholding taxes from your paycheck. Also, if you fail to meet the deadline for responding, you lose your right to appeal the original classification. Generally, it takes only a few hours to reply to a 30-day letter. You can use that time to find the information requested by your employer and get back to them with a response. If you want to reply by mail, then you should do so no later than 30 days after receiving the notice. They must receive your reply within this time frame, or else your response will not be considered. You cannot send your reply by courier service or through the postal system - only hand-carried mail is accepted. When you reply to a 30-day letter, make sure you write a clear message indicating whether you plan to appeal your classification or not. If you decide to appeal, then you must tell the employer who sent the letter about it.