1029.8.61.16. The person who, at a particular time in a particular month, becomes the cohabiting spouse of an eligible individual, in respect of an eligible dependent child, may, together with the eligible individual, elect, before the end of the eleventh month following the particular month, to be, in respect of any month subsequent to the particular month, deemed to have been the cohabiting spouse of the eligible individual throughout the period that began immediately before the end of the base year in relation to the particular month and that ended at the particular time.