How do I calculate actual home office costs as a sole trader instead of using the flat rate?

To claim actual home costs instead of the flat rate, you apportion your household bills based on the proportion of your home used for business and the proportion of time used. Step 1 — Calculate the space proportion: divide the number of rooms used for business by the total number of rooms in the home. A 4-bedroom house with a dedicated study = 1/5 (20%). Step 2 — Calculate the time proportion: how many hours per day, days per week is the room used for business? Example: 8 hours/day × 5 days/week = 40 hours out of 168 hours/week = 24%. Step 3 — Apply both: 20% × 24% = 4.8% of total household bills. Apply this percentage to your total annual costs for: gas, electricity, water (metered), council tax (if trading from home and property has business use), home contents insurance (business portion), rent or mortgage interest (not capital). Compare this figure against the flat rate to decide which gives the larger deduction.

  • Space proportion: business rooms ÷ total rooms in the home
  • Time proportion: business hours ÷ total hours in the week
  • Combined rate applied to: gas, electricity, water, council tax, rent/mortgage interest
  • Council tax is allowable only if HMRC accepts the property has mixed business/residential use
  • Calculate both flat rate and actual cost methods, then claim whichever is larger

Related Questions

  • How do I calculate the flat rate home office allowance for sole traders in the UK?
  • How do I claim use of home as office if I rent rather than own my property?
  • Can I claim my home broadband bill as a business expense if I work from home?