Many Buy To Let properties were purchased in individual names, that was norm before, then from 2017/18 we saw the introduction of clause 24 (section 24).
Essentially Section 24 removes Interest from the property expenses and gives you tax relief (finance allowance) at 20% (basic rate). So Higher rate tax payers will pay more tax.
Historically, its been common for BTL owners to regularly remortgage and with draw capital, basically cashing in on house price rises.
But what many owners seem to have overlooked is that if the mortgage exceeds the original property value (including SDLT and related costs) plus any improvement costs, then the mortgage interest is further restricted.
Increasing a mortgage
If you increase your mortgage loan on your buy-to-let property you may be able to treat interest on the additional loan as a revenue expense, as long as the additional loan is wholly and exclusively for the purposes of the letting business.
Interest on any additional borrowing above the capital value of the property when it was brought into your letting business is not tax deductible.
If the mortgage is for a residential property then the restrictions on interest from April 2017 will apply.Examples of how to work out Income Tax when you rent out a property – GOV.UK (www.gov.uk)