The records held by the National Portrait Gallery archive relating to Philip de László were received in three separate accessions: 1982/01, 2005/01 and 2011/01, a summary of the contents of each accession is as follows:
1982/01 consists of 19 photograph albums containing images of de László's portraits. The content of the albums is arranged chronologically, some albums span more than one year. The earliest album is annotated by de László 'Record of my works, 1916', further annotations by de László throughout the albums include sitter name and the date of work. The portraits documented in the albums were painted between 1903 and 1937.
2005/01 largely contains correspondence, including letters, postcards, telegrams, invitations, visiting cards and draft replies. It also contains press cuttings and other printed material, including some exhibition ephemera. The original order of these records which was devised by de László and his secretaries has largely survived. The records fall broadly into the following series: Personal correspondence 1892-1937; Family correspondence 1921-1936; Hungarian and German correspondence 1893-1937; Spanish, Portuguese and Italian correspondence 1894-1936; US correspondence 1927-1928; Court (royal) correspondence 1895-1916; Studio (portrait) correspondence 1891-1937; Press cuttings 1915-1933; Exhibition correspondence 1920-1936; Selected letters, mainly royal correspondence 1898-1935.
2011/01 consists of records relating to de László's internment during the First World War. It includes correspondence relating to de László's internment, including correspondence to Lucy de László; de László's written statement of defence to the Alien Advisory Committee; press cuttings and character witness statements in defence of the artist for the Naturalisation Committee, 1919. c. 1909-1919