In this episode of the I Hate Numbers podcast, we explore a tax trap that affects countless landlords and property investors. Preparing a property before tenants move in brings real costs, but HMRC applies strict rules on what you can and cannot claim. We explain those rules in plain English, highlight common mistakes, and show how to protect your cash flow and stay compliant.When Your Property Business Really StartsYour property business officially begins on the day your first tenant moves in and rent starts. That date matters because any spending before then is treated as pre-commencement expenditure. HMRC will only allow these costs if they meet three criteria:The cost must be within seven years of the start date.The cost must not already have been claimed elsewhere.The cost must be allowable if incurred after the business started.If all three conditions are met, the expense is treated as if it occurred on day one of the rental business.Understanding Revenue vs CapitalThis is the core of the tax decision. Revenue expenses repair or maintain the property without improving it. Examples include:RepaintingRepairing dampReplacing damaged flooring with similar materialsFixing broken boilers like-for-likeCapital expenses improve or upgrade the property. These include:ExtensionsLoft conversionsUpgrading to high-spec kitchens or bathroomsStructural alterationsRevenue costs reduce your rental profits now. Capital costs only reduce capital gains tax in the future.Examples That Show the DifferenceIf you treat dry rot or replace rotten timbers, HMRC sees it as a repair. If you convert a loft or add an extra bathroom, that improves the property’s overall value and is treated as capital. Understanding the difference prevents costly mistakes when completing your tax return.Why Record Keeping MattersHMRC expects clear records: invoices, breakdowns, and evidence of work carried out. Mixed invoices are a common issue. If repairs and improvements are bundled into one amount, HMRC may block the full claim. Ask contractors for itemised invoices, and take before-and-after photos to strengthen your position.Avoiding Common MistakesLandlords often run into trouble for reasons such as:Claiming costs older than seven years.Classifying improvements as repairs.Lacking itemised invoices or evidence.Using inconsistent accounting methods.If you have multiple rental properties, allowable repair costs from one property can still reduce overall rental profits across your portfolio.Episode Timecodes[00:00:00] Introduction[00:00:42] Understanding pre-letting costs[00:01:27] When a property business starts[00:02:00] The three tests for pre-commencement expenses[00:03:00] Revenue vs capital explained[00:04:12] Examples from real situations[00:05:00] What you can and cannot deduct[00:06:09] Record keeping and documentation[00:07:12] Mixed invoices and challenges[00:07:57] Accounting basis considerations[00:08:36] Impact on portfolios and holiday lets[00:09:18] Summary and next stepsFinal ThoughtsUnderstanding pre-let expenditure rules helps you avoid HMRC issues and protects your cash flow. The clearer your records and the more accurate your classifications, the smoother your tax return becomes. If you want personalised support reviewing your property costs, we can help with a detailed tax diagnostic review.Additional Links<a...