How UK postcodes work
Outward and inward codes, areas, districts and sectors — and why the format matters when you register.
A UK postcode has two halves. The outward code (for example M1 or SW1A) identifies the postcode area and district, and the inward code (for example 4AA) narrows it down to a sector and a small group of addresses.
PostDraw UK draws on the outward and inward code together, so the postcode you register must be a real, deliverable UK postcode. Areas are the letters at the start: M for Manchester, B for Birmingham, EH for Edinburgh, BT for Northern Ireland, and so on.
When you register, we check your postcode against our UK postcode database. If it is not recognised we flag it for our team to review rather than rejecting it outright, because new-build postcodes are added regularly.