Client (a sculpter) uses 2 rooms in her house for business for most of the day often working well into the evenings (not exclusive use rooms - the rooms do get used for other purposes like entertaining, guest room occasionally etc) total square footage of 2 rooms is 600 sq feet. House has 2 other reception rooms (500 sq feet in total), 4 bedrooms (1,000 sq feet), kitchen (150 sq feet), 2 bathrooms (180 sq feet) and corridors, halls etc (400 sq feet).
Total house floor space is 2,830 sq feet. Running costs of house are mortgage interest 4,000 plus utilities 2,000 plus council tax 2,500 total 8,500.
HMRC say you can apportion costs on a reasonable basis and gives examples.
Could you include the 2 rooms plus one bathroom and the corridors as all being used by the business so 1090 feet as a % of 2,830 so 38%?
Then for time allocation take 90% for the 2 main rooms which are used most of the time and 50% for the corridors and bathroom which are used from time to time during the day?