Not always. At my old postcode someone had recently built a block of flats not quite large enough to get its own postcode. The postcode also contained an older

Not always. At my old postcode someone had recently built a block of flats not quite large enough to get its own postcode. The postcode also contained an older block of flats and some houses. We were flat 9 but the postcode contained two flat 9s and a house number 9.