The information used to produce mortality statistics is based on the details collected when deaths are certified and registered.
In England and Wales, deaths should be registered within 5 days of the death occurring, but there are some situations that result in death registration being delayed. Deaths considered unexpected, accidental or suspicious will be referred to a coroner who may order a post-mortem or carry out a full inquest to ascertain the reasons for the death.
The coroner can only register the death once all investigations have concluded.
The time taken to investigate the circumstances of a death can often result in a death registration exceeding the 5-day grace period, leading to a delayed registration. While delays are commonly only a few days, they can extend into years.
This article (12.3 Kb Pdf) provides an overview of the impact of registration delays on data quality.