Which allowance you get, and why it matters
Buy equipment and you cannot simply deduct it like a normal expense — you claim capital allowances, and which one applies changes the timing enormously. Sometimes all of it lands this year; sometimes a fraction a year for a decade.
Full expensing gives 100% on new main-rate plant and 50% on new special-rate assets. It is uncapped and permanent, and it is for companies buying new and unused assets only. The Annual Investment Allowance gives 100% on up to £1,000,000 a year, covers both pools, and is open to unincorporated businesses and to second-hand kit. For most practices the AIA does everything full expensing would have.
In this sector the spend that matters is typically vans, tippers, plant and excavators, power tools, scaffolding, welding gear and site accommodation.
The sole trader / limited company split matters most here
Full expensing is for companies only. If you are a sole trader or a partnership — which most trades still are — it is not available to you at all, and the Annual Investment Allowance is your route. That is not a problem: the AIA covers £1,000,000 a year and gives you the same 100% relief below that level.
It only starts to matter above a million a year of qualifying spend, which is a different conversation entirely.
A van is plant. A pickup might not be.
Vans and lorries are plant and qualify. Cars are excluded from both the AIA and full expensing and run on their own CO2-based rules. Double-cab pickups sit in the middle and their treatment has changed — the classification that used to make them attractive no longer works the way it did, so check before you buy one on the strength of old advice.
Buying second-hand?
Plenty of good plant is bought used, and used kit does not qualify for full expensing. It does qualify for the Annual Investment Allowance, so for most trades buying second-hand the relief is identical. Worth knowing before somebody talks you into new on tax grounds alone.