Can nonprofit organizations still be liable for other state and local taxes, even if the organization has a valid sales and use tax exemption certificate?

Yes. The Maryland sales and use tax exemption certificate applies only to the Maryland sales and use tax. A nonprofit organization that is exempt from income tax under Section 501(c)(3) or Section 501(c)(19) of the Internal Revenue Code, and holds a valid Maryland sales and use tax exemption certificate, is still be liable for other state and local taxes in Maryland, such as local hotel taxes.