By the start of the Second World War in 1939, considerable spending on increasing Britain's military capacity had already taken place. The rearmament programme, which had begun in the mid-1920s, was costing £197 million by 1937.
In 1938 the standard rate of income tax was increased to 5s 6d (27.5 per cent), with a 41 per cent surtax on incomes over £50,000. Some 10 million people were by now paying direct taxation.
During the war the rate of income tax increased even further in order to keep pace with vast expenditure needs. In the budget of 1941, however, the promise of 'tax credits' was introduced in order to make the increasing load more bearable to the taxpayer.
In 1944 the PAYE system ('pay as you earn') was introduced whereby tax was deducted from wages by employers each week or month. Now that millions of workers were paying income tax, this new scheme allowed tax to be collected more efficiently than previously when tax was collected annually or twice yearly.