But what makes the NICs regime especially opaque is the employers' part of national insurance, not least because the incidence of NICs falls squarely on employees - either through lower wages or higher unemployment. Indeed, study after study has shown that when countries increase their payroll taxes, it leads to a reduction in pay, not a reduction in profit.
This is not to say that the burden is lifted entirely from employers. An extensive Taxpayers' Alliance study in 2011 argued that administration alone imposes a £146m compliance cost on businesses and places a particularly heavy burden on smaller companies, which need to hire accountants to help them cope with the system. It also incentivises employers to hire temporary staff when, all things being equal, they would prefer to bring them into the business as PAYE employees.