Finance directors of businesses with high annual levels of capital expenditure on plant and machinery were probably pleased to hear the Chancellor announce a temporary increase in the annual investment allowance (AIA) from £200,000 to £1,000,000 for the two calendar years 2019 and 2020 at Budget 2018.

Some may have sighed slightly and reflected that life would be easier if the AIA limit was stable and only subject to occasional upward revision but they would at least have understood the implications of the temporary increase.

Consider, by contrast, the reaction of a typical decision-maker in an owner-managed business.