The ceiling on expenditure qualifying for the Annual Investment Allowance was to have fallen from £250,000 to £25,000 on 1 January 2015.
Instead it is increased to £500,000 for expenditure incurred between 1 April 2014 (6 April 2014 for income tax) and 31 December 2015.
After which (1 January 2016) it will reduce to £25,000
For any business looking to invest in plant and machinery (not cars) this means that you can offset the first £500,000 of capital spend against trading profits.