D.C. Code § 28-5402
Prohibited practices.
(a) Beginning January 1, 2025, a retailer shall not discriminate against cash as a form of payment for goods or services, including by:
(1) Refusing to accept cash as a form of payment;
(2) Posting signs on the premises that cash payment is not accepted; or
(3) Charging a higher price to consumers who pay cash.