Originally Posted by WindFlyer
Call the same place you booked them (the UA international awards desk). They'll let you know all the details (mailing them in, airport exchange, etc..).
And yes, the $100 is a 'processing fee'.
If you have paper tickets it is best to do at the airport where they can credit the miles back to your account on the spot and apply for the tax refund.
BTW the award fees are waived for 1K/UGS on United. Last week I was mistakenly charged the $100 fee for redepositing the miles but I have already disputed it with my credit card company. (Don't have time to call United refunds regarding this.)