These prefixes are used for UK and Crown Dependency (CD) amateur callsigns, unless otherwise stated suffixes may be one, two or three characters in length:

• Foundation M3, M6, M7 + three character suffix
• Intermediate 2#0, 2#1, M8, M9 + three letter suffix, two letter suffix 2#0/2#1 calls were issued in 2018-19
• Full G0, G1, G2, G3, G4, G5, G6, G7, G8, M0, M1, M5 + three letter suffix, two letter suffix calls issued prior to 2020
• Short Contest Callsign with single character suffix, format Gnx or Mnx where n=0-9 and x=A-Z
• Special Event Station MB5 issued in 2015 now format is GBnccccl, MBn where n=numeral, c=numeral, letter or null, l=letter suffix may be 1-4 characters or no suffix at all e.g. GB50 issued in 2002
• Analog Voice Repeaters GB3 + two letter suffix
• Digital Voice Repeaters GB7 + two letter suffix
• Beacons GB3 + three letter suffix
• Gateways/Data Stations MB7 + two or three letter suffix

If a callsign starts with 2 a Regional Secondary Locator must be inserted immediately after the 2 e.g. 2E0ABC for a station in England. For G and M callsigns the use of a RSL is entirely optional

On 13 October 2025 Ofcom stopped issuing new Intermediate callsigns with a “2” prefix. Exist holders of “2” prefix callsigns were allowed to select their existing suffix from the M8 (for 2#0) or M9 (for 2#1) call series alternatively they could select any available callsign they liked from the M8 or M9 series.

From 13 October holders of Full callsigns who'd been licenced for more than 5 years were allowed to change to any available Full series prefix callsign e.g. G3, G5, M5 and Foundation holders were allowed to change to another call in the M3, M6 or M7 call series. A number of bugs in Ofcom's online system meant a delay of a couple of weeks before that could be done.

Calls available for issue include those callsigns that have been in the Reserved state for more than 5 years as indicated by the Last Modified Date field in Ofcom's callsign spreadsheet (A blank date field also means it's more than 5 years old). To get one of these callsigns amateurs need to ring Ofcom or use Ofcom's online chat and ask them to change the status to available.

Ofcom Guide to Changing your Callsign Online

The prefixes of UK callsigns have changed considerably over the past century, the regional prefixes we have today only exist because at various times the RSGB made representations to the regulator to create them. Prior to the 1990's the term “Regional Secondary Locator” (RSL) wasn't used, either “Callsign Prefix” or “Callsign Zone” were used instead.

Up until July 1991 UK amateur callsigns used only the G prefix. The introduction of the Novice (Intermediate) licence saw the use of the 2 prefix, it may well be this change triggered the use of the term “Regional Secondary Locator” instead of Prefix.

September 1989 RadCom reported the RSGB had suggested to the then regulator, the DTI, the use of the “M” prefix for Novice callsigns but “2” was eventually chosen by the new regulator, the Radiocommunications Agency (RA) in 1991

These three QSL cards illustrate the variations the club station of the Stirling and District Amateur Radio Society had in the space of just 10 years: G-6NX, GC-6NX, back to G-6NX, then GM-6NX. Thanks to GM6DX for images

In 1927 UK formally obtained the country prefixes of M, G, and 2 from the ITU (G had been used by UK amateurs prior to 1927). The ITU also issued the UK with V and Z prefixes which were used in the Dominions and Empire. From Spring 1927 the UK used G prefix callsigns for England, Wales and CD's, GC prefix for Scotland (prefix believed to to voluntary rather than mandatory), GI for Northern Ireland and GW for the Irish Free State.

Prefixes were discussed in the July 1936 issue of the RSGB T & R Bulletin. At the time amateurs in the UK and Crown Dependencies had just two prefixes, either G which covered Great Britain & CDs and GI for Northern Ireland. The GC prefix used briefly in Scotland in the mid-1920's had reverted back to G around 1929 and the former GW prefix, used for the Irish Free State, had been replaced by EI.

The view was expressed in the Bulletin that both Scotland and the Channel Islands should be counted as a separate entities with a unique prefix but it was not felt the Isle of Man deserved a unique prefix and Wales was regarded as an integral part of England, so should have the same prefix. However, within a few months the RSGB would shift its position regarding a Welsh prefix

In 1937 at the request of the RSGB the regulator, the General Post Office (G.P.O), introduced prefixes GM for Scotland and GW for Wales.

In 1946 the G.P.O agreed to an RSGB request to create the prefix GC for the Channel Islands, December 1946 T & R Bulletin

In 1947 the RSGB changed its mind over a prefix for the Isle of Man and asked the G.P.O. to create one, June 1947 T & R Bulletin

In 1977 at the request of the RSGB the Channel Island GC prefix was replaced by GU for Guernsey and GJ for Jersey leading to the creation of a new DXCC entity for amateurs to collect, December 1976 RadCom

In 1995 new RSL's were introduced for Club stations, they could be used to identify those stations permitted to send Greeting Messages from unlicenced persons, a facility introduced at the same time, but the use of the Club specific RSL's was optional and many clubs stuck to the RSL they'd always used.

In 2000 Short Contest Callsigns with MZ and GZ prefixes were introduced for use in the Shetland Islands, RSGB December 2000 RadCom announcement

In 2008 Ofcom said they did not regard the RSL as being part of the core UK callsign and in 2013 stated the words in the licence actually meant the Main Station RSLI should be used when visiting other regions but they were happy for amateurs to continue with existing practice of changing RSL if they wished.

In 2014 Ofcom proposed making it clear in the licence that the RSL was optional, this generated opposition from the RSGB so Ofcom decided not to add clarity to the licence at that time but Ofcom continued to consider that amateurs with M or G callsigns could either omit the RSL or give the RSL for the region they were visiting if they wished.

In 2014/15 an attempt was made by Cornish amateurs to get the “K for Kernow” RSL issued for use in Cornwall. While Ofcom appeared to be supportive of the idea and issued a temporary “K” RSL during 2016 but the RSGB did not support a permanent “K” RSL and it did not happen https://web.archive.org/web/20160408145201/https://gb2gm.org/k-for-kernow/ : Poldu report on RSL

Correspondence from Ofcom and RSGB

In 2023 Ofcom again proposed changing the licence words to make it clear the RSL was optional.

In August 2025 RSGB Director Stewart Bryant G3YSX posted this explanation:

At the request of the RSGB the regulator agreed to the use of these special RSL's for a limited period.

From 4 June to 12 June 1977 all UK licensees were allowed to use the prefix “GE” instead of the normal country prefix, to commemorate the Silver Jubilee of Her Majesty, Queen Elizabeth II.

From 5 May to 12 May 1985 the GV prefix was used from all parts of the UK in the period . The prefix was used to celebrate the 40th anniversary of the end of WWII (“Peace in Europe” according to QSL cards). The GV prefix was used for special event calls, not personal calls (unlike the GE & GQ prefix). The “V” possibly signified Victory.

During December 2001 the three character callsign “2MT” was used by the Chelmsford Amateur Radio Society special event station set up at the Marconi factory in New Street, Chelmsford, Essex, to commemorate Marconi's first trans-Atlantic wireless transmission. The station used all Marconi Equipment. This is believed to be the only example of a Special Event Callsign with a “2” prefix. Unlike Intermediate “2” calls it was permitted full legal power and didn't require the use of an RSL. 2MT had been used in 1922 for the UK's first regular entertainment broadcasts which were made from Writtle.

During the whole month of June 2002, all UK licensees were allowed to use the prefix “GQ”, “MQ” or “2Q”, as appropriate, instead of the normal country prefix, to commemorate the Golden Jubilee of Her Majesty, Queen Elizabeth II. Also during this period, the special callsign “GB50” was used by a commemorative station set up at Windsor Castle, England. This callsign was unique in that it did not contain any suffix letters.

From 1 September 2009 to 20 October 2010, special event stations commemorating the centenary of the Girl Guide movement could request callsigns in the GG100xx or GG100xxx series.

From 29 April 2011 to 09 May 2011 the prefixes “GR”, “MR” & “2R” were allowed, via online application for an NoV, to be used by individuals as special temporary calls to celebrate the Royal Wedding of H.R.H Prince William to Miss Catherine Middleton. Club special calls for this event were of the standard “GB” type, although, due to administrative errors, some Clubs applied and were issued the NOV but were not allowed to use it.

From 9-11 October 2015 special event station MB5RC was run by Kenwood UK at the RSGB Convention

Source: Highfields Amateur Radio Club

Ofcom stores callsigns in their licensing database in the base format for the UK, the Regional Secondary Locator (RSL) is not regarded as part of the call sign for Regulatory purposes.

Ofcom will no longer issue callsigns with the suffixes listed in the Forbidden Suffixes spreadsheet, however, in the past some of them have been issued

• Ofcom Forbidden callsign suffixes 5 December 2024

Callsign spreadsheet issued on 11 November 2025 three weeks after the release of M8/M9 callsigns for Intermediate and all categories of amateur being able to change their callsign

• Ofcom Callsign Spreadsheet 11 November 2025

Callsign spreadsheet issued prior to the release of M8/M9 callsigns, gives Status, Last Modified Date and Original Start Date

• Ofcom Callsign Spreadsheet 11 September 2025

All Amateur callsigns in Ofcom's database includes Special Event Station callsigns (GB/MB calls) and Special Research Permits e.g. high power

• Ofcom Callsign Spreadsheet 17 September 2024

Callsign spreadsheet issued before the February 2024 re-issue of all licences. Ofcom's licence re-issue forced an update of the Last Modified Date Field for all valid licences. Sorting on the Last Modified Date field can give you an indication of how many amateurs had actually revalidated their licences since 2006 as revalidation forces a change to Last Modified Date

• Ofcom Callsign Spreadsheet 11 January 2024

An easy way to see at a glance which callsigns are available is to use the M0PYL Callsign Lookup. Note: All callsigns marked as Reserved with a Date Last Modified of either blank or more than 5 years old are available for issue, you just need to ring Ofcom and ask them to change it to Available status

• M0PYL Callsign Lookup

A list showing the approximate issue year of amateur radio callsigns up until 2000 is available at

• RF-Man Amateur Radio Callsigns

The Original Start Date for callsigns issued after 1977 is available in the Ofcom Callsign Spreadsheet dated 11 September 2025. Due to an administrative glitch by the then Regulator that date field is not reliable prior to 1977.

For failure to revalidate every 5 years

As of November 2025 Ofcom had only ever revoked amateur licences on one occassion for failure to revalidate in the previous 5 years. It occurred in October-November 2015 when Ofcom did a test run of their month-long revocation procedure. For the test a small batch of licences that had not been revalidated in the previous 8 years were put into the 30-day revocation appeals process, the licence holder was contacted and if after 30 days they hadn't said they wished to keep the licence then Ofcom revoked it. In total 530 licences were revoked out of the aproximately 14,500 licences that had not been revalidated in the previous 8 years - list of the callsigns that were revoked

Ofcom found the revocation procedure was labour-intensive and expensive they never repeated the exercise, no further licences were revoked.

In the May 2017 issue of Practical Wireless the Editor Don Field G3XTT mentioned that Ofcom had quietly dropped the idea of revoking unvalidated licences.

In 2024 Ofcom signalled an intent to revoke licences that hadn't been revalidated in the previous 5 years. It the same year Ofcom automatically revalidated every single licence, this meant no licence would need revalidation until 2029 at the earliest.

In January 2024 there had been some 63,000 unvalidated licences, many hadn't even been validated once in the previous 18 years. If Ofcom do what they have indicated then there will be a sudden drop in licence numbers in 2029/30.

When there's a licence upgrade or a Callsign change

As of October 2025 if you upgrade or change your callsign then your lower-level licences will be put into the 30 day revocation procedure during which time should you wish to keep the licence you can appeal the decision to revoke. At the end of that period if no appeal is submitted the licence will be revoked.

ITU Radio Regulations Article 19 Section III − Formation of call signs:

19.45 § 21 1) The twenty-six letters of the alphabet, as well as digits in the cases specified below, may be used to form call signs. Accented letters are excluded.

19.46 2) However, the following combinations shall not be used as call signs:

19.47 a) combinations which might be confused with distress signals or with other signals of a similar nature;

19.48 b) combinations in Recommendation ITU-R M.1172-0 that are reserved for the abbreviations to be used in the radiocommunication services. (WRC-15)

19.68 1) – one character (provided that it is the letter B, F, G, I, K, M, N, R or W) and a single digit (other than 0 or 1), followed by a group of not more than four characters, the last of which shall be a letter, or – two characters and a single digit (other than 0 or 1), followed by a group of not more than four characters, the last of which shall be a letter. (WRC-03)

19.68A 1A) On special occasions, for temporary use, administrations may authorize use of call signs with more than the four characters referred to in No. 19.68. (WRC-03)

19.69 2) However, the prohibition of the use of the digits 0 and 1 does not apply to amateur stations.

ITU Radio Regulations Article 19 Identification of a Station

RF-Man UK Callsign page Shows approximate date callsigns first issued

Short Wave Magazine April 1949 page 134 (PDF page 56) Callsigns in the 1920's