Unfortunately, we are unable to provide personal tax advice in relation to your BTL property, and you will need to speak to an accountant who can advise you based on your personal circumstances.
At completion, the property will be subject to Stamp Duty Land Tax "SDLT", you can use HMRC's calculator here to calculate the SDLT due.
You may also be liable for council tax should your property be unoccupied, and you will need to speak to your local council to found out how much, and in what circumstances you're expected to pay.