Self-assessment holds up where the building is small and simple, the fire risks are ordinary, nobody sleeps on the premises and the escape routes are short and obvious. A single-storey shop, a small office or a modest workshop sits comfortably in this territory. Government guidance was written precisely so that owners of premises like these could work through the five steps without buying in help.
Even in easy territory the duty comes with conditions. Since Section 156 of the Building Safety Act 2022 took effect, the whole assessment has to be written down, findings and measures included, whatever the size of the organisation. Competence also includes knowing where your knowledge stops: identifying a question you cannot answer, such as whether an escape route is acceptable, is the signal to take advice rather than guess.