Postcode district boundaries:
|Coordinates: 51°27′58″N0°01′55″W / 51.466°N 0.032°W|
|Postcode area name|
|Statistics as at May 2020 |
The SE (South Eastern) postcode area covers a broad radial swathe of the south-east of the London post town from the Albert Embankment to West Heath and the nearest edges of Sidcup and Selhurst. It loosely corresponds to the boroughs of Southwark, Lewisham and Greenwich plus indicated parts of the boroughs of Croydon (north), Lambeth (east), Bexley (west) and Bromley (its northwest corner).
The postcode area originated in 1857 as the SE district. In 1868 it gained some of the area of the short-lived S district, with the rest going to SW. It was divided into numbered districts in 1917, by giving the district closest to London that hosted the head office the suffix "1" and all others alphabetically based on a locally important parish, chapelry, topological or built environment feature administering or close to the local distribution office.  SE28 is a late addition carved out of the existing districts SE2 and SE18 to reflect the building up of a new London district in what had been the meadows and marshes by the tidal Thames in the parish of Plumstead: Thamesmead.
Unlike SW, where a consecutive 50%, there ten, districts can more officially be traced into two alphabetical groups excluding SW1, SE has always technically followed the norm in that SE1 is the only head district. However SE19 was drawn up to serve the key distribution office serving Norwood after a complete alphabetical series so that those surrounding it and SE21 (Dulwich): SE20 and SE22 to SE27 are strictly alphabetical afresh (Anerley to West Norwood) but it has never technically been a "head district".  The postcode area is part of the London post town.  There are no dependent localities used in the postcode area.  SE1P is a non-geographic postcode district for PO boxes located in SE1. 
The approximate coverage of the postcode districts, with the historic postal district names shown in italics: 
|Postcode district||Post town||Coverage||Local authority area(s)|
|SE1||LONDON||South Eastern head district: Bankside, South Bank, Lambeth (part), Southwark, Bermondsey (part), Vauxhall (part), Peckham (part)||Lambeth, Southwark|
|SE2||LONDON||Abbey Wood district: Abbey Wood, West Heath, Crossness, Thamesmead (part), Plumstead (part), Bostall Heath and Woods||Greenwich, Bexley|
|SE3||LONDON||Blackheath district: Blackheath, Kidbrooke, Westcombe Park||Greenwich, Lewisham|
|SE4||LONDON||Brockley district: Brockley, Crofton Park, Ladywell, Telegraph Hill||Lewisham|
|SE5||LONDON||Camberwell district: Camberwell, Denmark Hill, Peckham||Lambeth, Southwark|
|SE6||LONDON||Catford district: Catford, Bellingham, Hither Green (part), Rushey Green||Lewisham|
|SE7||LONDON||Charlton district: Charlton||Greenwich|
|SE8||LONDON||Deptford district: Deptford, Evelyn, Rotherhithe (part), St John's||Lewisham, Greenwich, Southwark|
|SE9||LONDON||Eltham district: Eltham, Mottingham, New Eltham, Well Hall, Avery Hill (part), Falconwood (part), Sidcup (part), Chinbrook (part), Longlands (part) Kidbrooke (part), Shooter's Hill (part)||Greenwich, Bromley, Bexley, Lewisham|
|SE10||LONDON||Greenwich district: Greenwich, Maze Hill, Greenwich Peninsula||Greenwich, Lewisham|
|SE11||LONDON||Kennington district: Kennington, Lambeth (part), Vauxhall (part), Oval (part)||Lambeth, Southwark|
|SE12||LONDON||Lee district: Lee, Mottingham, Grove Park, Chinbrook, Hither Green (part), Eltham (part), Horn Park||Lewisham, Greenwich, Bromley|
|SE13||LONDON||Lewisham district: Lewisham, Hither Green, Ladywell||Lewisham, Greenwich|
|SE14||LONDON||New Cross district: New Cross, Telegraph Hill||Lewisham|
|SE15||LONDON||Peckham district: Peckham, Nunhead, South Bermondsey (part)||Southwark, Lewisham|
|SE16||LONDON||Rotherhithe district: Rotherhithe (part), Surrey Quays, South Bermondsey (part)||Southwark, Lewisham|
|SE17||LONDON||Walworth district: Walworth, Kennington (part), Newington||Southwark|
|SE18||LONDON||Woolwich district: Woolwich, Royal Arsenal, Plumstead, Shooter's Hill||Greenwich|
|SE19||LONDON||Norwood district: Upper Norwood, Crystal Palace, Gipsy Hill (part)||Croydon, Lambeth, Southwark, Bromley|
|SE20||LONDON||Anerley district: Anerley, Crystal Palace (part), Penge, Beckenham (part)||Bromley|
|SE21||LONDON||Dulwich district: Dulwich, Dulwich Village, Tulse Hill (part), West Dulwich||Southwark, Lambeth|
|SE22||LONDON||East Dulwich district: East Dulwich, Peckham Rye||Southwark|
|SE23||LONDON||Forest Hill district: Forest Hill, Honor Oak, Crofton Park (part), Perry Vale||Lewisham, Southwark|
|SE24||LONDON||Herne Hill district: Herne Hill, Tulse Hill (part), West Dulwich (part)||Lambeth, Southwark|
|SE25||LONDON||South Norwood district: South Norwood, Selhurst (part), Thornton Heath (part), Woodside (part)||Croydon|
|SE26||LONDON||Sydenham district: Sydenham, Crystal Palace (part)||Lewisham, Bromley, Southwark|
|SE27||LONDON||West Norwood district: West Norwood, Gipsy Hill (part), Tulse Hill (part)||Lambeth|
|SE28||LONDON||Thamesmead district: Thamesmead||Greenwich, Bexley|
SE1 has a very long tidal Thames frontage and is in Central London as is SE11 named after Kennington, close to Westminster. SE2–SE18 spread across the north and east of the postcode area; enquiring into their naming system explains how SE2, SE7, SE8, SE10, SE16 and SE18 also front the river. Postcode districts SE19–SE27 form a group in the southwest. Addition SE28 is in the northeast corner of the first group. The postcode area maps roughly to the combined area of the London Borough of Southwark, London Borough of Lewisham and Royal Borough of Greenwich. the eastern part of the London Borough of Lambeth, the northern part of the London Borough of Croydon, the western part of the London Borough of Bexley and the northwestern part of the London Borough of Bromley are within the postcode area.
In 2002, some residents in West Heath, a slight projection with neighbouring areas, wished to have their postcodes changed from SE2 to the adjacent DA7 postcode district, citing higher insurance for their houses, belongings and cars as reasons to change. Royal Mail has said it will not consider changes to postcodes for these reasons. 
Postal codes used in the United Kingdom, British Overseas Territories and Crown dependencies are known as postcodes. They are alphanumeric and were adopted nationally between 11 October 1959 and 1974, having been devised by the General Post Office. A full postcode is known as a "postcode unit" and designates an area with several addresses or a single major delivery point.
The London postal district is the area in England of 241 square miles (620 km2) to which mail addressed to the London post town is delivered. The General Post Office under the control of the Postmaster General directed Sir Rowland Hill to devise the area in 1856 and throughout its history it has been subject to reorganisation and division into increasingly smaller postal units, with the early loss of two compass points and a minor retraction in 1866. It was integrated by the Post Office into the national postcode system of the United Kingdom during the early 1970s and corresponds to the E, EC, N, NW, SE, SW, W and WC postcode areas. The postal district has also been known as the London postal area. The County of London was much smaller, at 117 square miles (300 km2), but Greater London is much larger at 607 square miles (1,570 km2).
The W postcode area, also known as the London W postcode area is a group of postcode districts covering part of central and part of West London, England. The area originates from the Western (W1) and Paddington (W2-14) districts of the London postal district. This area covers 35 postcode districts and around 18,554 live postcodes.
The E (Eastern) postcode area, also known as the London E postcode area, is the part of the London post town covering much of east London, England. It borders the N postcode area to the west, both north of the tidal Thames. Since closure of the East London mail centre its mail is sorted at Romford Mail Centre together with IG and RM postcode areas.
The IG postcode area, also known as the Ilford postcode area, is a group of eleven postcode districts in England, within six post towns. These cover parts of eastern Greater London and south-west Essex. Inward mail for the area is sorted, along with mail for the E and RM postcode areas, at the Romford Mail Centre.
The EC postcode area, also known as the London EC postal area, is a group of postcode districts in central London, England. It includes almost all of the City of London and parts of the London boroughs of Islington, Camden, Hackney, Tower Hamlets and Westminster. The area covered is of very high density development. Deliveries for the EC postcode area are made from Mount Pleasant Mail Centre.
The WC postcode area, also known as the London WC postcode area, is a group of postcode districts in central London, England. The area covered is of high density development, and includes parts of the City of Westminster and the London Boroughs of Camden and Islington, plus a very small part of the City of London.
The SM postcode area, also known as the Sutton postcode area, is a group of seven postcode districts in England, within five post towns. These cover part of south-west London, as well as a small part of north Surrey.
The BR postcode area, also known as the Bromley postcode area, is a group of eight postcode districts in England, within seven post towns. These cover part of south-eastern Greater London, as well as a small part of north-west Kent.
The TW postcode area, also known as the Twickenham postcode area, is a group of twenty postcode districts in south-east England, within thirteen post towns. These cover parts of south-west London and north-west Surrey, plus a very small part of Berkshire.
The DA postcode area, also known as the Dartford postcode area, is a group of eighteen postcode districts in England, within eleven post towns. These cover parts of south-east London and north-west Kent.
The UB postcode area, also known as the Southall postcode area, is a group of eleven postcode districts in England, within six post towns. These cover parts of western and north-western Greater London, plus a very small part of Buckinghamshire. The letters in the postcodes are the phonemic abbreviation of Uxbridge.
The WD postcode area, also known as the Watford postcode area, is a group of eleven postcode districts in Greater London and Hertfordshire, within seven post towns. These cover south-west Hertfordshire, plus very small parts of Buckinghamshire and the London Borough of Hillingdon.
The DN postcode area, also known as the Doncaster postcode area, is a group of 32 postcode districts in England, which are subdivisions of 13 post towns. These cover eastern South Yorkshire, north Lincolnshire, small parts of Nottinghamshire and the East Riding of Yorkshire, and a very small part of North Yorkshire.
The NW postcode area, also known as the London NW postcode area, is a group of 13 postcode districts covering around 13,895 live postcodes within part of northwest London, England. It is the successor of the NW sector, originally created as part of the London postal district in 1856.
The NE postcode area, also known as the Newcastle upon Tyne postcode area, is a group of 61 postcode districts in north-east England covering 34 post towns. These cover most of Tyne and Wear and Northumberland, plus a very small part of northern County Durham. The NH postcode area is one of six with a population above 1 million.
The N (Northern) postcode area, also known as the London N postcode area, is the part of the London post town covering part of North London, England. It is a group of 25 postcode districts which covers around 17,429 live postcodes.
The G postcode area, also known as the Glasgow postcode area, is a group of postcode districts in central Scotland, within five post towns. These districts are primarily centered on Glasgow itself, and West Dunbartonshire, plus parts of the council areas of Argyll and Bute, East Dunbartonshire, North Lanarkshire, South Lanarkshire, East Renfrewshire and Stirling.
The SW postcode area, also known as the London SW postcode area, is a group of 20 postcode districts within the London post town in England. The area comprises the South Western operational district and the Battersea operational district, and is the only area within the London post town to lie on both sides of the River Thames.