Md. Code, Commercial Law § 12–504

(a) Notwithstanding any other statutory law, a seller, financial institution, or the successor in interest of either may charge, collect, and receive under a retail credit account a finance charge, however described, not to exceed the amounts permitted in §§ 12-505 and 12-506 of this subtitle.

(b) If the date of performance or delivery of an item or service is more than 10 days from the date of purchase, the finance charge shall be computed from the date of performance or delivery.