D.C. Mun. Regs. tit. 31, § 806
806.1 When the driver does not have available sufficient currency to change a large bill in payment of the fare, the driver shall inform the passenger of that fact while enroute to the passenger's destination, and ask whether change will be required. The driver shall inform the passenger of the charge for making change pursuant to § 806.4.
806.2 If the passenger states that change will be required, the driver shall stop enroute and provide an opportunity to change the bill in question. No charge for the stop shall be permitted.
806.3 A Commission approved sign that is displayed within the passenger's view, stating that the operator can only change a designated bill, may be considered as notice to the passenger of the operator's limitation on making change.
806.4 If the driver has informed the passenger of the lack of change as set forth in § 806.1 and the passenger presents the driver, at the destination, with a bill requiring change which the driver is unable to provide, the driver may allow the meter to continue running (or reset the meter if it has been stopped) to take the passenger to obtain change and return to the passenger's original destination. The passenger must pay the total fare.
806.5 In no other circumstances shall a charge be imposed for deviations or stops required in order to obtain change.
SOURCE: Final Rulemaking published at 37 DCR 3595, 3616 (June 1, 1990); as amended by Final Rulemaking published at 59 DCR 9970, 9974 (August 17, 2012).