The White House on Tuesday abruptly announced a one-year delay, until 2015, in his health care law’s mandate that larger employers provide coverage for their workers or pay penalties. The decision postpones the effective date beyond next year’s midterm elections. The 2010 Affordable Care Act required employers with more than 50 full-time workers to offer them affordable health insurance starting next year or face fines. Some companies with payrolls just above that threshold said they would cut jobs or switch some full-time workers to part-time employment so that they could avoid providing coverage. Under the provision to set up state-based marketplaces, subsidies are supposed to be available to many lower- and middle-income people who do not have access to coverage from employers or other sources. It may be difficult, however, for officials running the exchanges to know who is entitled to subsidies if employers do not report information on the coverage they provide to workers.