The 1861 Worldwide Army Index which is also known as The 1861 Worldwide Soldier Index, includes the extraction of some 245,000 serving soldiers listed in the National Archives April-June quarter Paylists held in WO 10 (Royal Artillery), WO 11 (Royal Engineers) and WO 12 (Cavalry, Guards, Infantry and other units) series War Office records. It includes records not only of other ranks of soldiers serving in Britain, but also men serving in Queen Victoria's Army far-flung empire outposts. For this reason, it can be an exceptionally useful source in identifying men missing from the 1861 England, Wales & Scotland census returns.

The index provides the names, ranks, army numbers and regiments of about 98% of other ranks subjects serving in the British Army. A small number, estimated at about 5000 men, are not included because the Paylists listing their names have not survived.

If a man aged 14-18 years or older cannot be found in the 1861 England, Wales & Scotland census, or the findmypast collection in British Army Service Records 1760-1915, then consulting the 1861 Worldwide Army Index is essential. Once candidates have been located they can then be further researched in National Archives records. Whilst soldiers listed in the 1861 Worldwide Army Index will only be seen to be serving in one quarter of 1861, they may nevertheless have been serving as early as 1840 or might have continued in service up to as late as 1882.