In 1975 and 1976 Ps filed separate income tax returns, checking the status box entitled 'married filing separately.' In computing their respective tax liabilities they applied the rates in I.R.C. §1(c) for 'Unmarried individuals' rather than the higher rates prescribed by §1(d) for 'Married individuals filing separate returns.' P consulted with the United States Attorney for the Eastern District and with members of the Intelligence Division of D, explaining that he and his wife wanted to challenge the constitutionality of the 'marriage penalty' without incurring liability for fraud or willfulness. Following these conversations they filed their returns as described, attaching to each return a letter explaining that, although married, they were applying the tax tables for single persons because they believed that the 'income tax structure unfairly discriminates against working married couples' in violation of the equal protection clause of the fourteenth amendment. The Tax Court rejected this constitutional challenge, sustaining D's determination that the Ps were subject to tax at the rates provided in §1(d) for married persons filing separately. Both parties appealed.