With respect to merchandise sold at a museum gift shop, the IRS rules that where the primary purpose of the activity and merchandise is to further the organization's exempt purpose, the sale is considered related and thus not subject to unrelated business income tax (UBIT). Where the primary purpose is to generate income, there is the potential that the activity is subject to UBIT.
The IRS has taken the position that an art museum's gift shop sales of interpretive teaching items with artistic themes furthered the museum's educational purpose. Thus, items that develop artistic ability were considered substantially related to the museum's educational purpose and thus not subject to UBIT. Also, items clearly for the convenience of the patrons, such as food or beverage are not subject to UBIT.