Since the enactment of the net investment income tax ("NIIT") in 2012, physicians and other taxpayers owning multiple business interests have had to make educated choices based upon accounting projections and SWAGS when determining how best to treat ancillary businesses for tax purposes. If an ancillary business is treated as an active trade or business or is otherwise required to be"grouped" with the physician's regular practice under the passive activity rules, the income and/or loss generated by the ancillary business will be treated as ordinary income or loss, and will not be subject to the NIIT. On the other hand, if the physician has unused passive losses from other business investments, being able to treat an ancillary business which actually produces income as a "passive" activity, produces the better income tax result by allowing the passive losses to offset that passive income. The most important decision though comes when the ancillary activity is first acquired and "grouped" with other active or passive activities since that grouping must also be used in subsequent years (absent a material change in facts and circumstances). Treas. Reg. Section 1.469-4(e).