Fetching details from the dictionary...
head of the family (esp. as recorded in the resident register); head of the household; householder
世帯主の名前を記入してください。
Please write the name of the head of household.
世帯主が変わると届け出が必要だ。
A notification is required when the head of household changes.
住民票には世帯主との続柄が記載されている。
The resident card lists the relationship to the head of household.