Background: Regular clinical care is important for the well-being of people with HIV. We sought to audit and describe the characteristics of adults with diagnosed HIV infection not reported to be attending for clinical care in the UK. Methods: Public Health England (PHE) provided clinics with lists of patients diagnosed or seen for specialist HIV care in 2010 but not linked to a clinic report or known to have died in 2011. Clinics reviewed case-notes of these individuals and completed questionnaires. A nested case-control analysis was conducted to compare those who had remained in the UK in 2011 while not attending care with individuals who received specialist HIV care in both 2010 and 2011. Results: Among 74,418 adults living with diagnosed HIV infection in the UK in 2010, 3510 (4.7 %) were not reported as seen for clinical care or died in 2011. Case note reviews and outcomes were available for 2255 (64 %) of these: 456 (20.2 %) remained in the UK and did not attend care; 590 (26.2 %) left UK; 508 (22.6 %) received care in the UK: 73 (3.2 %) died and 628 (27.8 %) had no documented outcome. Individuals remaining in the UK and not attending care were more likely to be treatment naïve than those in care, but duration since HIV diagnosis was not significant. HIV/AIDS related hospitalisations were observed among non-attenders. Conclusion: Retention in UK specialist HIV care is excellent. Our audit indicates that the 'true' loss to follow up rate in 2011 was <2.5 % with no evidence of health tourism. Novel interventions to ensure high levels of clinic engagement should be explored to minimise disease progression among non-attenders.