Under hire purchase the asset goes onto your balance sheet at the outset, with a corresponding liability for the amount owed to the lender. You then depreciate the asset over its useful life, and each monthly payment is split between reducing the liability and charging interest to your profit and loss account. It is accounted for as a purchase funded by borrowing.
So the monthly payment does not appear in your profit and loss as one line. The capital element reduces what you owe. The interest element is a finance cost in the period it relates to. The depreciation charge is separate again, driven by your own depreciation policy rather than by the payment schedule.
Any deposit or part exchange at the start reduces the amount financed. Where the agreement has a balloon payment at the end, the liability runs down more slowly across the term because a larger slice of the capital is deferred to the final payment — worth planning for in your cash flow, not just your accounts.
The tax figures then diverge from the accounting figures: depreciation is added back and capital allowances are claimed instead. That reconciliation is standard work for your accountant, but it is the reason the tax deduction and the accounting charge rarely match in any given year.
This is general information, not tax advice. Confirm your own position with your accountant or HMRC.