Parts of it usually are, but not all of it, and how much depends on the type of agreement. On most hire purchase and lease purchase deals the interest element is treated as a business expense and the asset may qualify for capital allowances. On leases and contract hire, the rentals are normally the deductible cost. Your accountant should confirm the split.
The point that catches people out is that the monthly payment is not a single deductible number. Under hire purchase you are treated as the buyer from the start, so the capital part of the payment is not an expense — instead the asset goes into your accounts and you claim capital allowances on it, while the interest and any fees are expensed as they arise.
Under an operating lease or contract hire you never own the asset, so there is nothing to capitalise and no capital allowances to claim. The rental is treated as a running cost of the business. Some assets — cars in particular — carry a restriction on how much of the rental you can deduct. That restriction is tied to the car’s CO2 emissions, and both the emissions threshold and the proportion disallowed are set by government and revised from time to time, so check the position for your accounting period on gov.uk rather than assuming last year’s.
Whether any of this reduces your bill also depends on whether the business is profitable, how it is structured, and its accounting period. Relief on a deduction is given at your prevailing tax rate, so the same expense is worth different amounts to different businesses. We arrange the funding; we do not advise on the tax outcome.
This is general information, not tax advice. Confirm your own position with your accountant or HMRC.