Regulation 3 Meaning of “frontier worker”
A person is a frontier worker for the purposes of these Regulations if they were, immediately before IP completion day, and have been continuously since IP completion day—
an EEA national;
not primarily resident in the United Kingdom; and
either—
a worker in the United Kingdom;
a self-employed person in the United Kingdom; or
a person treated as a worker or self-employed person in the United Kingdom by virtue of regulation 4.
For the purposes of paragraph (1), it does not matter if a person changes from one of the statuses in paragraph (1)(c) to another.
For the purposes of paragraph (1), a person is to be treated as not being primarily resident in the United Kingdom at a particular point in time (“the relevant date”) if—
they have been present in the United Kingdom for less than 180 days in the twelve-month period immediately before the day on which the relevant date falls; or
they have returned to their country of residence at least—
once in the six-month period immediately before the day on which the relevant date falls; or
twice in the twelve-month period immediately before the day on which the relevant date falls,
unless there are exceptional reasons for not having done so.