Maryland has adopted legislation enacting single sales factor apportionment for calculating Maryland corporate income tax. (L. 2018, H1794 (c. 342) and L. 2018, S1090 (c. 341), effective July 1 and applicable to all taxable years beginning after Dec. 31, 2017.) Beginning with tax year 2018, the single sales formula used to apportion income to Maryland will be phased in over a five-year period. By tax year 2022, all multistate corporations subject to income tax, with the exception of certain worldwide headquartered companies, will use a 100 percent sales factor.