Online purchases will be taxed starting today. Michigan’s new Main Street Fairness Law kicked in Thursday, that means big name on line retailers including Amazon will start collecting 6% sales tax. Previously, consumers were supposed to self report the sales tax if the retailer didn’t automatically charge it. About 117,000 people reported untaxed online purchases on their 2013 tax returns, paying $6.7 million in sales tax. State officials estimated that represented only 2.5% of what was really due