Md. Code, Local Government § 20–201

(a) This section applies to a political subdivision of the State that is

authorized to impose a sales tax.

(b) Except as part of the imposition of a sales tax generally on business

transactions and businesses, a political subdivision may not impose a sales tax on

advertising transactions or advertisers.

(c) A political subdivision may not impose a sales tax on advertising

transactions or advertisers at a rate that exceeds the rate under a sales tax imposed

generally on other business transactions or other businesses by the political

subdivision.