About 14 percent of families that filed tax returns for 2014 reported a spell of uninsurance for at least one family member. Uninsurance rates were higher for young adults, unmarried persons, low-income families, and families in states that did not expand eligibility for Medicaid. These results are generally consistent with estimates from survey data. Many families who were uninsured in 2014 appear eligible for Medicaid or Premium Tax Credits. Outreach to these families could effectively reduce the number of uninsured. Better data for 2015 and later years will allow for more comprehensive and detailed estimates about uninsured Americans.