Repairs to Commercial Property

If a business rents a commercial property and has to replace part of the concrete floor in the warehouse to enable continued operations, would this be an allowable expense?

If I understand you correctly, you are a tenant who runs a business from premises that you rent from a landlord, and you have to pay for the repair of the concrete floor. Your question is: is this payment an allowable business, revenue, expense that you can offset in full in the current year against your business profits? If you look on page PIM2020 on the HMRC Property Income Manual

http://www.hmrc.gov.uk/manuals/pimmanual/PIM2020.htm you can see that a repair of a part of the structure of a property, when the replacement can be classified as ‘like for like’, i.e. without a significant upgrade or improvement to what was there originally, can be treated as a revenue, allowable business expense. This can be true even if the repairs are substantial.