The ORCiD author identifier system is now being implemented by universities across the UK, and by many publishers and funding organisations to help manage researchers' journal articles and other published outputs. Digital object identifiers – DOIs – are also now widely used to uniquely identify research publications. But are ORCiD and DOI identifiers also being used for PhD students and their theses? Or are doctoral theses lagging behind more formally published papers when it comes to identifiers? And if so, why is that? In 2015, the Unlocking Thesis Data project (UTD) brought together the Universities of East London and Southampton, DataCite, and the British Library's EThOS e-theses service, to explore DOIs and ORCiDs for doctoral theses. This paper will describe the level of identifier adoption for research students and theses in the UK, and the work of the UTD project to encourage their use. The project also examined the range of supplementary material and data resulting from doctoral research – and the potential use of identifiers to manage these outputs. As a result of UTD, a small number of UK theses now have DOIs and/or ORCiDs and there are many encouraging signs of wider uptake by universities, students and research organisations.