My two pennies.
The way we work is changing, and even when I consider my parents' generation (those born in the forties) things couldn't be more different. For starters, permanent contracts are mostly limited to the public sector, and even there things are shifting. Gone are the days of 'a job is for life'; we are a people on the move, changing employer frequently, country and even career. And it's not just the 'recession's fault'. I think at the heart of the matter there is the need to step back from the Monday to Friday routine, the commute to the office and the countless memes about how much we hate Mondays. More often we find ourselves looking up to those countries where they only work four days a week, and wish we were there. And we should be. In case you haven't noticed, and even if you live a healthy full 90 years of life, it doesn't amount to too much in the grand scale of human evolution. So why should we waste our pitiful handful of years doing something that feels like a drag just so we can pay, pay and then pay some more, to the disadvantage of our wellbeing? I am confident that people wouldn't 'hate' their job, or Mondays, if they had a more balanced work/personal time life. They day I went down to four days a week (thanks to Tijaran Tales), I felt like another person. I started enjoying every day I had and stopped wishing my life away (I wish it was Friday... I wish it was summer...). In fact, when Luna Press came to life, time started to accelerate in a frightening manner, and I began to wish I had more hours in the day and that time would slow down (never happy, are we?).
Rant over.
The internet has given us the chance to change the way we work. Private companies keep their employees at home, working and talking to each other remotely. It saves money all around, and it means that the individual can make better use of those hours which would have been otherwise spent in commuting. And when your work is done, you are more inclined to get out for a walk and to be more sociable, or at least is how I find it. I couldn't recommend it enough.
Back to claiming expenses.
Authors can work from home (from wherever really), and even though most will also have another job to pay the mortgage, the home becomes their place of work. And that is good because it means they can claim expenses for it.
As always, I'm not a tax-man, just someone who does the tax return every year. Check the tax website of your country and don't get caught out.
There are two primary ways to claim expenses, the simplified expenses method and the proportion of home method. Knowing what they entail, will help you decide which is best for you.
For the purpose of comparison let's assume that you write 4 hours per day, so an average of 122 hours a month.
Simplified expenses method
This is the easiest of the two, saving you time and headaches when it's time to do your tax return. It uses a flat rate instead of actual business costs. You must be working from home a minimum of 25 hours a month in order to use this method.
If you work between: 25-50 hours a month, you can claim £10 p/m 51-100 hours a month, you can claim £18 p/m 100+ hours a month, you can claim £26 p/m
Remember that the flat rate doesn’t include telephone or internet expenses. You can claim the business proportion of these bills by working out the actual costs.
Since you write 100+ hours a month, you are entitled to £26x12=£312 plus a proportion of your phone/internet bill.
Proportion of Home Method
I hope you kept your yearly bills handy and ready for inspection. Costs can include: Heating, Electricity, Council Tax, Rent / Mortgage interest (just the interest part of your payments, not the capital), Home insurance, Water, Phone and internet (you can add these in with your office costs total, though I would keep them separate as they are not really related to the space you use, so the percentage of business use might be different).
The important thing is to find a reasonable way to do your calculations, and stick to it. One such way could be to divide your total costs by the number of rooms used for business and by time spent working from home.
Example:
You have 4 rooms in your home, one of which you use only as your office. You write 4 hours per day, which is 1/6 of the day (24 hours / by 6 = 4 hours of writing per day)
Your total bills for the year come to £800.
£800/4 rooms = £200
£200/6= £33.33
£33.33 x 12 months = £400 and that is your actual proportions of expenses.
Comparison
It is often the case that the Proportion of Home Method gives back more than the simplified expenses, but it really comes down to you: have you got all the bills filed and ready for inspection should they ask you, and are you bothered with the calculations?
As always with these things, I can only set you on the right path, but it's up to you to make sure you are ready for your tax return.