You may be entitled to a refund on Income Tax or Corporation Tax paid in the last 1 or 2 financial year and reduce your tax burden in the current and subsequent financial years. If you do not claim the money is simply lost over time. More of your profit will go to the government than it needs to in the form of overpaid Income Tax or Corporation Tax.
As an example, a property in the hospitality sector, on average, has capital allowances of 32% of its value built up within it over time. For a £500,000 property that is £160,000 of allowances UNUSED that have built up over time. If you own your property in your own name that could be a £64,000 refund waiting for you.