Three changes of note were announced in the 2018 budget, each with different implementation dates;
1. The special writing down allowance rate has been reduced from 8% to 6% from 1/6 April 2019. This mainly applies to motor vehicles with CO2 emissions greater than 110g /km, integral fixtures and fittings and long life assets.
2. The cynical amongst you might think that this has occurred in order to pay for the new structure and buildings allowance (SBA) for expenditure on or after 29 October 2018 and will be given at a straight line rate of 2% on new shops, hotels, farms and offices as well as industrial units. On sale the remaining relief available transfers to the new owner.
3. The annual investment allowance has been increased from £200,000 to £1,000,000 for qualifying expenditure incurred between 1 January 2019 and 31 December 2020. But do be aware of the pitfalls. Where an accounting period straddles the 31 December 2020, and a company acquires a qualifying asset on say 1 February 2021 for £60,000 it will in fact only be able to claim 90/365 x £200,000 = £49,315 irrespective of the fact that might be their only capital expenditure in the whole of the year 1 April 2020 to 31 March 2021. HMRC are not sympathetic to this unfair result – you should get the timing right seems to be their attitude.