“The IRS said it did not need to go through that assessment because only large employers — defined as businesses that employ 50 or more people — are required under the healthcare law to either provide workers with health insurance or pay a fine. But Sargeant and his assistant chief counsel, Dillon Taylor, said the act of a small business assessing whether or not it should comply with the regulation — and the paperwork it must keep in case it does — impose a heavy burden.”