The National Identification Authority, which registers Ghanaians and resident foreign nationals and issues the Ghana Card.
Registration happens at NIA district offices and premium registration centres. The NIA has run registration by district and by region, so which office is correct depends on when you are reading this — check before you travel.
Bring proof of citizenship, your GhanaPostGPS digital address, and if you have neither a passport nor a birth certificate, two Ghanaian guarantors with valid cards, in person.
Keep the confirmation slip you are given. It is your only evidence that registration happened, and many institutions accept it while you wait for the card.