Two ways you can claim for carrying out business admin at your home. 

Yes, business owners can claim the expense of using their home as an office, (as a business expense), based on the portion of rent, mortgage interest, council tax, water, fuel etc. used while working on the business at home, rather complicated!  

There are 2 ways to calculate this: 

Weekly Claim Business owners spending small amounts of time, say, invoicing or doing minimal work relating to the business can claim £4 per week (or £18/month) without calculating the actual home expenses used. 

Actual Expenses:  If the owner spends, say, a few hours each day at home running the business, they can claim a proportion of actual home expenses. (Rent, rates etc. as above) 

If you use the 2nd method; HMRC provide examples online – but they are complex.  I recommend that you ask your accountant to do the calculation.