Apportionment of expenses

[xoAmyox]

I am looking to rent out one bedroom in my 3 bed house (its the second bedroom - if that makes any difference?)
How would I reasonably apportion my expenses (bills, mortgage interest etc) for my tax return, I dont want to over or under-estimate and get in trouble!

Also, how do I go about sorting out the expenses for furnishing the room for the first time, and ongoing replacement/repair of the furnishings (its empty at the moment)

Thanks!

[Telometer]

How much will the annual rent be?

[xoAmyox]

It should be between £4,200 and £5,400 depending on whether I have a couple or a single person in there.

[Telometer]

You should almost certainly go on the rent a room scheme. This provides that the first £4,250 of receipts (including contributions to utilities/council tax etc) is free of tax. The balance is taxed at your marginal rate. It will almost certainly give a better result than the actual calculation would, and it will save you a whole load of record keeping too.

www.hmrc.gov.uk/individuals/tmarent-a-room-scheme.shtml