Parking will cost a reduced rate of $27 per day with tax. There will be no in and out. If you are staying at the hotel, let them know you are with IBPA at check-in in order to get the reduced rate. If you are not staying at the hotel, you can pick up a sticker for your parking ticket at the IBPA registration desk on the 5th floor. You can also use the site below to browse for different parking options.
https://spothero.com/chicago/chicago-mariott-downtown-magnificent-mile-parking