Home Business Sales and Use Tax Special Situations Modular Buildings Modular Buildings Sales of modular buildings are subject to Maryland's 6 percent sales and use tax and the rate is applied to 60 percent of the taxable price. A "modular building" would include: Single-family or multifamily houses; Apartment units; Commercial buildings; and Certain permanent additions to single-family or multifamily houses, apartment units, or commercial buildings. The permanent additions are taxable if they are comprised of one or more sections that are: Intended to become real property; Primarily constructed at a location other than the permanent site at which they are to be assembled; Built to comply with the standards for industrialized buildings under Title 12, Subtitle 3 of the Public Safety Article; and Shipped with most permanent components in place. If your average tax liability for out-of-state purchases is more than $100 per month, you are required to report and remit the tax every month. If your tax liability is less than $100 per month, you may file on a quarterly basis.