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 IT hardware, case management infrastructure, desks and furniture, meeting room fit-out and archive storage.
An LLP is not a company for this
Full expensing is available to companies within the charge to corporation tax. A traditional partnership or an LLP taxed as a partnership does not get it, and uses the Annual Investment Allowance instead — £1,000,000 a year, both pools, new or second-hand.
For most firms that is the same answer in practice. It stops being the same answer on a large fit-out, which is precisely when the difference is worth several thousand pounds.
Office fit-out: two pools, not one
Desks, chairs, screens, servers and the coffee machine are main-pool plant. The lighting, the wiring, the air conditioning and any floor or ceiling forming part of those systems are integral features at 6%. On a floor refit the integral features are usually the bigger number, and they are the ones worth pointing the AIA at first.
Software is its own question
Case management and practice management software may be plant and machinery, or it may be an intangible fixed asset relieved through the accounts — the treatment depends on how it is licensed and capitalised. It is worth settling at the point of purchase, because the two routes give very different timing.