You do not need to do anything after you have mailed the amendment in. 3 weeks after mailing your amended return, you can start tracking it at the IRS Where's My Amended Return? tracking tool. Please allow at least 16 weeks for the IRS to process your amended return. Processing times for amended state returns vary from state to state. If it's been more than 12 weeks since you mailed your amended state return, and you haven't heard anything, we suggest you contact your state tax agency.