Example: Assume that the taxpayer meets the requirements of this paragraph for the years 1967 through 1971, and that the taxpayer, whose wife died during 1966 while married to him, remarried in 1968. In 1969, the taxpayer's second wife died while married to him, and he remained single thereafter. For 1967 the taxpayer will qualify as a surviving spouse, provided that neither the taxpayer nor the first wife was a nonresident alien at any time during 1966 and that she (immediately prior to her death) did not have a taxable year different from that of the taxpayer. For 1968 the taxpayer does not qualify as a surviving spouse because he remarried before the close of the taxable year. The taxpayer will qualify as a surviving spouse for 1970 and 1971, provided that neither the taxpayer nor the second wife was a nonresident alien at any time during 1969 and that she (immediately prior to her death) did not have a taxable year different from that of the taxpayer. On the other hand, if the taxpayer, in 1969, was divorced or legally separated from his second wife, the taxpayer will not qualify as a surviving spouse for 1970 or 1971, since he could not have filed a joint return for 1969 (the year in which his second wife died).
if such person has a gross income of less than the amount determined pursuant to § 1.151-2 applicable to the calendar year in which the taxable year of the taxpayer begins, if the taxpayer supplies more than one-half of the support of such person for such calendar year and if such person does not make a joint return with his spouse for the taxable year beginning in such calendar year. The taxpayer may not be considered to be a head of a household by reason of any person for whom a deduction is allowed under section 151 only by reason of sections 152 (a)(9), 152 (a)(10), or 152(c) (relating to persons not related to the taxpayer, persons receiving institutional care, and persons covered by multiple support agreements).
26 C.F.R. §1.2-2