Easy online tools to register and start a business in Maryland, register a trade name in Maryland and establish tax accounts in Maryland. Are you looking for business assistance or considering Maryland as a location?Guide on MD sales tax for online sellers. The Comptroller of Maryland offers many online services to make filing a Maryland tax return easy, convenient, and fast. An e-commerce retailer's guide on how to register for, collect, and file sales tax in Maryland in order to stay compliant. To file or pay your taxes, visit the Maryland Tax Connect portal, use an independent software provider, or a professional tax preparer. To determine if you need a license, contact your local Clerk of the Circuit Court or call the State License Bureau at 410-260-6240.