Flexible benefits, often called a "flex scheme", is where employees are allowed to choose how a proportion of their remuneration is paid or they are given a benefits budget by their employer to spend. Currently around a third of UK employers operate such a scheme. How flexible benefits schemes are structured has remained fairly consistent over the years, although the definition of flex has changed quite a lot since it first arrived in the UK in the 1980s. When flex first emerged, it was run as a formal scheme for a set contract period, through which employees could opt in and out of a selection of employer-paid benefits, select employee-paid benefits, or take the cash. In recent years increasing numbers of UK companies have used the tax and national insurance savings gained through the implementation of salary sacrifice benefits to fund the implementation of flexible benefits. In a salary sacrifice arrangement an employee gives up the right to part of the cash remuneration due under their contract of employment. Usually the sacrifice is made in return for the employer's agreement to provide them with some form of non-cash benefit. The most popular types of salary sacrifice benefits include childcare vouchers and pensions.