Unless an act that changes the State income tax rate provides otherwise, if the rate changes on a date other than the 1st day of the taxable year of a person, the person shall compute State income tax using the tax rate that applies to each part of the year.
Md. Code Ann., Tax-Gen. § 10-603
Official source: Maryland General Assembly. Reproduced from public-domain Maryland statutes; confirm against the official source for the current text. Not legal advice.