UK Naturalisation Records for Polish-Born Ancestors

A UK naturalisation certificate is the document that made a foreign national a British subject (from 1949, a citizen of the United Kingdom and Colonies). For a Polish-born ancestor it usually gives their full name, address, place and date of birth, parents’ names, occupation, and the names of a spouse and dependent children. Before 1918, Poles appear under the country that ruled their home region, so look for “Russia”, “Germany” (Prussia) or “Austria” as well as “Poland”.

The National Archives at Kew holds naturalisation records up to 30 September 1986, and most can be found by name in its free Discovery catalogue. Grants were also announced in The London Gazette, while certificates issued from 1 October 1986 are held by UK Visas and Immigration. This guide explains each series, what a file can tell you about your family in Poland, and how to ask for files that are still closed.

How Poles became British subjects

Before 1844 naturalisation needed a private Act of Parliament, which was expensive, so few people used it. From 1844 the Home Office granted naturalisation, and the Naturalisation Act 1870 and the British Nationality and Status of Aliens Act 1914 set the rules for most of the period that matters to Polish families. The British Nationality Act 1948 then created citizenship of the United Kingdom and Colonies from 1 January 1949.

Polish-born people arrived in several waves, and each left a slightly different paper trail:

Before the First World War: emigrants from the Russian partition (including many Jewish families), from Prussian Poland and from Austrian Galicia. They were legally Russian, German or Austrian subjects, and the records say so.
Between the wars: citizens of the new Polish state, who appear as “Poland” in the indexes and the Gazette.
After the Second World War: soldiers, airmen and sailors of the Polish Armed Forces, many of whom passed through the Polish Resettlement Corps, their families and displaced persons. The Polish Resettlement Act 1947 supported their settlement in Britain, and many later naturalised. Our guide to Polish veterans’ resettlement in Britain explains that stage.

One trap: a foreign woman who married a British subject before 1 January 1949 was deemed British on marriage, so she may have no naturalisation record of her own. Look for her husband’s file instead.

The main National Archives series

The National Archives research guide lists these as the key series. The ones in bold are the most useful for Polish ancestors.

Series	Dates	What it holds	Access
HO 334	1870–1986	Duplicate naturalisation certificates (not kept for certificates issued in the UK from June 1969)	Searchable by name in Discovery; 1870–1916 images on Ancestry (paid)
HO 409	1908–1980	Home Office indexes to certificates; the only source of detail from June 1969 to 1980	Searchable by name in Discovery
HO 1	1801–1871	Early naturalisation case papers and correspondence	Searchable and downloadable (charge) from Discovery
HO 45, HO 144, HO 382	1872–1934	Naturalisation case papers	Search Discovery by name followed by nat*
HO 405	Arrivals 1934–1948	Case files of foreign nationals, mostly European, who later applied to naturalise	Searchable by surname; 100-year closure, but you can ask for access under FOI
C 54 / C 275	1844–1873	Enrolments on the close rolls and their printed index	At Kew only

Denization, a more limited status, is recorded in Chancery patent rolls such as C 67. It is rarely relevant to Polish families, most of whom arrived after 1850.

Searching Discovery

Search the surname followed by nat* (for example “Nowak nat*”) and sort the results by date.
Try every plausible spelling: Wiśniewski may be catalogued as Wisniewski, Wisnievski or Visnevsky, and Russian-era files often use a transliteration of the Cyrillic form.
Search the anglicised name as well. HO 405 files record name changes, but the catalogue entry may use either form.
Note the certificate number from HO 409 or HO 334. It is the quickest way to order copies.

What a naturalisation certificate and case file contain

The certificate is short but precise. According to The National Archives it usually gives the full name, address, place of birth, age or date of birth, parents’ names, spouse’s name, occupation and the names and ages of dependent children. From June 1969 to 1980, when no duplicates were kept, the HO 409 index entry (name, residence, certificate number and date of issue) is all that survives.

The case file is the application behind the certificate, and it is far richer. Depending on the period it can contain:

the application form with nationality, date and exact place of birth, and address history in the UK;
names and ages of the spouse and children;
character references from British referees;
a police or mayor’s report on the applicant (from about 1878);
in HO 405: visa applications, employment permits, name changes, papers on internment during the Second World War and later correspondence, mostly up to the mid-1960s;
for ex-servicemen, possibly details of service in the Polish Armed Forces and the Polish Resettlement Corps.

The National Archives says only about 40% of the applications in HO 405 have survived. If there is no file, the certificate and index entry are still worth having.

The London Gazette notices

Grants of naturalisation were published in The Gazette, and The National Archives points researchers to it for the years 1844 to 1980. The lists give the name, the country of former nationality, the date of the oath of allegiance, occupation and place of residence. The notices are free to search online by name.

The Gazette confirms the date of the oath, which is when naturalisation took effect, and shows how the Home Office recorded the person’s origin. A 1914 list, for example, has applicants from “Russia”, “Germany” and “Austria”, several of whom may have been born in what is now Poland.

Closed files, later certificates and how to request them

HO 405 files still under closure

HO 405 files are closed for 100 years unless the catalogue says otherwise. If the entry shows the file as closed, you can ask The National Archives to review it under the Freedom of Information Act, using the request option on the Discovery entry or its FOI enquiry form. The file may then be released in full, in part or not at all. Give the full catalogue reference and any evidence that the person has died.

Certificates from 1949 to 30 September 1986

Naturalisation certificates from 1949 to 1980 are found through HO 334 and HO 409 in Discovery. For registration certificates issued in the UK from 1 January 1949, and naturalisation certificates issued in the UK from 1 January 1981, up to 30 September 1986, The National Archives runs a certificate search service for people born less than 100 years ago. The initial search is free and results are sent within 10 working days. At the time of writing (September 2026), a certified copy costs £68.84 plus postage; the price of a standard copy depends on the number of pages.

From 1 October 1986

The National Archives does not hold certificates issued after 30 September 1986; contact UK Visas and Immigration instead. The GOV.UK service to replace a citizenship certificate is for people who became British after 30 September 1986 and costs £456 at the time of writing (September 2026). UKVI cannot issue replacements for people who became British before October 1986; GOV.UK directs them to The National Archives.

Certificates kept by the family

Before you order anything, check family papers. Original certificates often survive with passports, service documents and Polish identity papers, and the certificate number takes you straight to the HO 334 or HO 409 entry and, from there, the case file.

Worked example (illustrative)

Take an invented case: “Jan Kowalski”, a former corporal of the Polish Armed Forces living in Bradford. The family has no certificate, only a memory that he “became British in the fifties”.

A Discovery search for “Kowalski nat*” brings up an HO 409 index entry with a certificate number and a date in the 1950s, and an HO 334 duplicate certificate.
The certificate gives his birth in a village near Tarnów in 1915 and his parents as Józef and Maria.
The Gazette confirms the date of his oath of allegiance.
A search of HO 405 by surname finds a closed file with his date of birth, so the family asks for it to be reviewed under FOI, sending his death certificate.
With the village, parish and parents’ names, the next step is his baptism or civil birth entry in Poland.

From the British file to Polish records and citizenship evidence

A naturalisation file often gives the clue Polish research needs most: the exact place of birth. With the parents’ names (including, with luck, the mother’s maiden name), a date of birth and military details, you can go straight to the right parish or civil register in Poland. Our guide to finding a birth entry in Poland explains that step. For ex-servicemen, the file can also point to service records held by the Ministry of Defence.

The file matters just as much for Polish citizenship by descent. Under the Polish citizenship act of 20 January 1920 (in force from 31 January 1920 until 18 January 1951), a Polish citizen generally lost Polish citizenship by acquiring a foreign one. People obliged to perform active military service were an exception: they needed the permission of the Minister of Military Affairs, and without it the Polish state continued to treat them as Polish citizens. Under Article 13, a loss of citizenship also extended to the person’s wife and children under 18, unless the minister decided otherwise.

The act of 8 January 1951, in force from 19 January 1951, took a different approach: a Polish citizen could acquire a foreign citizenship only after obtaining the Polish authorities’ permission to change citizenship. Naturalising abroad without that permission is generally understood not to have ended Polish citizenship under this act, but how it applies depends on the facts of each case.

This is why the date of naturalisation, the person’s military status at the time and the position of their wife and children are important evidence. Two families with almost identical stories can get different results depending on whether the oath was taken before or after 19 January 1951. The 1920 act was also amended several times, and later laws and court rulings affect how it is applied today. How these rules apply to your family is a legal question, so take advice from a lawyer who specialises in Polish citizenship before you apply. Our overview of Polish citizenship for British citizens sets out the background, and building a citizenship evidence file explains how to organise the British and Polish documents.