This question was answered on 14th October 2015
On 25th June 2015 the Department for Work and Pensions published the report “Income-related benefits: Estimates of take-up in 2013/14 (experimental)”. The full report can be found at:
https://www.gov.uk/government/statistics/income-related-benefits-estimates-of-take-up-financial-year-201314
For Great Britain, the following estimates are available for 2013/14:
- Income Support, and Employment and Support Allowance: between 510,000 and 650,000 benefit units are estimated as not claiming Income Support, and Employment and Support Allowance, an unclaimed caseload proportion of 19% to 23%, and estimated to be valued between £2.43 billion and £3.25 billion unclaimed;
- Pension Credit: between 1.24 million and 1.43 million benefit units are estimated as not claiming Pension Credit to which they are entitled, an unclaimed caseload proportion of 36% to 39%, and estimated to be valued between £2.48 billion and £3.26 billion unclaimed;
- Housing Benefit: between 1.11 million and 1.3 million benefit units are estimated as not claiming Housing Benefit, an unclaimed proportion of 18% to 21%, and estimated to be valued between £3.16 billion and £4.1 billion unclaimed; and
- Jobseeker's Allowance: between 650,000 and 820,000 are estimated as not claiming Jobseeker’s, an unclaimed proportion of 39% to 45%, and estimated to be valued between £1.99 billion and £2.62 billion unclaimed.