Objectives: We aimed to update the estimated prevalence of both diagnosed and undiagnosed chronic hepatitis B virus infection in Denmark. Moreover, we aimed to determine the number of people with chronic hepatitis B virus infection in specialised care and to assess the completeness of reporting to the national register of communicable diseases. Methods: Using four registers with national coverage, we identified all individuals registered with chronic hepatitis B virus infection, aged 16 years or older, and alive in Denmark on 31 December 2016. The diagnosed population was then estimated using capture-recapture analysis. The undiagnosed population was estimated using data from the Danish pregnancy screening program. Results: We estimated that 14,548 individuals were living with chronic hepatitis B virus infection corresponding to 0.3% of the Danish population. Of them, 13,530 (93%) were diagnosed and 7942 (55%) were registered in one or more of the source registers. Only 4297 (32%) diagnosed individuals had attended specialised care and only 3289 cases (24%) were reported to the Danish communicable disease register. Conclusion: The prevalence of chronic hepatitis B virus infection increased from 2007 to 2017. The majority that had been diagnosed did not receive care as recommended by national guidelines and were not reported to the communicable diseases register responsible for hepatitis B virus surveillance. Future efforts should focus on linking individuals diagnosed with chronic hepatitis B virus infection to specialised care and improving reporting to the hepatitis B virus surveillance system.