they record what they see your ethnic origin as and what you describe yourself as. If they're stopping a white person, they write IC1 in the IC box, there's a Self Defined Ethnicity (SDE) box that to fill in they have to ask you what you would describe yourself as. You then pick from a list, eg. White Irish or White British. If it was a black person they would write IC3 and there SDE might be Black African or Black Caribbean or something else.
they record what they see your ethnic origin as and what you describe yourself as. If they're stopping a white person, they write IC1 in the IC box, there's a Self Defined Ethnicity (SDE) box that to fill in they have to ask you what you would describe yourself as. You then pick from a list, eg. White Irish or White British. If it was a black person they would write IC3 and there SDE might be Black African or Black Caribbean or something else.