Sorry the machine is down

The City of Chicago requires that all non-independent taxis accept credit cards. (almost all cabs in the city are affiliated) However, when trying to pay with a credit card it is not uncommon for the driver to say something like "Sorry the machine is down," especially if they believe that you may be a tourist. It is however, considered polite and fair, as it does cost them to process the card, to pay in cash for short (ie. less than 15$) trips. If you can only pay with credit consider adding a dollar or two to the tip.