To ask the Chancellor of the Exchequer, pursuant to the Answer of 26 November 2018 to Question 194204 on Brexit and with reference to paragraph 4.111 of the Office for Budget Responsibility's Economic and Fiscal Outlook published in October 2018, what proportion of the £400 million underspend relates to the UK leaving the EU.
On 13 March 2018, the Treasury confirmed allocations of c.£1.6bn to departments. A full breakdown of the allocation can be found in the Chief Secretary’s Written Ministerial Statement, HCWS540, laid on 13 March https://www.parliament.uk/business/publications/written-questions-answers-statements/written-statement/Commons/2018-03-13/HCWS540/.
The Economic and Fiscal Outlook is produced by the independent Office for Budget Responsibility (OBR). As part of their fiscal forecast they take a judgement on how much departments will underspend on aggregate DEL spending. Further information on how the OBR reach their judgement is available at https://obr.uk/forecasts-in-depth/tax-by-tax-spend-by-spend/departmental-expenditure-limits/.