What the Work-From-Home Expense Tracker does
This tracker apportions household costs to home working: it takes each bill as you are actually billed for it - weekly, monthly, quarterly or annually - converts it to a monthly figure, and applies the share of your home and the share of your time that the work genuinely uses. It shows the arithmetic for every line, so the claim can be checked rather than believed.
It deliberately contains no tax rules and no allowances. Whether a cost is deductible at all, whether a flat rate is available instead, and how an employee's position differs from a sole trader's are decided by your country's tax authority and your employer's policy. What this page does is the part that is the same everywhere: work out defensibly what proportion of each bill belongs to work.
How to use it
- Enter either the number of rooms used for work against the rooms in your home, or the work area against the total floor area. Both may be entered; choose one method per cost and use it consistently.
- Enter the hours you work at home each week and pick the denominator: 168 for the whole week, or your own waking-hours figure. Choose "no time share" only if the space is used for nothing but work.
- Add each bill with the amount as billed and the billing period. Set how it should be apportioned - by rooms, by area, at a fixed percentage you decide, wholly business, or not claimed.
- Read the monthly and period claim, and check each line's share in the table.
- If your tax authority publishes a flat monthly allowance, type it into the comparison box to see which method gives more.
Reading the results
The share column is space share x time share x business-use factor. Multiplying the bill by that number gives the claim for the line - nothing else is applied.
The time share only touches costs apportioned by rooms or area. A fixed percentage you have decided, and a wholly business cost, are taken as final.
"Share of the bills claimed" is the whole claim over the whole of the bills entered. Over about 40% is unusual for a home worker and the page says so.
The flat-rate comparison is only meaningful with a published rate for your country and year. Nothing is assumed, and no rate ships with this page.
Worked example: a spare room used three days a week
A five-room home with one room used for work gives a space share of 1/5 = 20%. Working 22.5 hours a week against the full 168-hour week gives a time share of 22.5/168 = 13.3929%. Multiplied together the share is 2.6786%.
The bills are electricity at 96 a quarter (32 a month), gas at 78 a quarter (26 a month), broadband at 32 a month and contents insurance at 180 a year (15 a month) - 105 a month between them. At 2.6786% that is exactly 2.8125 a month, or 33.75 a year.
A separate business phone line at 15 a month is marked wholly business and claimed in full, so the total is 17.8125 a month and 213.75 over twelve months.
For comparison, a flat allowance of 26 a month would give 312 - about 98 more. That is common: flat rates are generous for part-time home workers with small bills, and poor for anyone running a business from a large share of their home.
Formulas and scoring rules
- Monthly cost
monthly = amount x factorfactor is 52/12 for weekly, 1 for monthly, 1/3 for quarterly and 1/12 for annual bills.- Space share
rooms used / rooms total, or work area / total area- Time share
working hours per week / hours denominator168 for the whole week, or your own waking-hours figure. Not applied to fixed-percentage or wholly business lines.- Claim per line
claim = monthly x space share x time share x business useBusiness use defaults to 100% and is only reduced if you set it.- Period claim
period = monthly claim x months claimedAt most twelve months in a year.
Rooms or floor area?
The room-count method is simpler and is what most people use: one room of five is 20%, whatever their sizes. The area method is fairer when the work space is unusually large or small - a 4 m2 corner of an 88 m2 flat is 4.5%, not the 25% a four-room count would suggest.
Whichever you pick, keep it for the whole claim and record which one you used. The commonest objection to a home-working claim is not the arithmetic but the inconsistency: rooms for the costs where rooms give more, area for the rest.
Why the hours matter as much as the space
A room used for work for 22.5 hours a week is not a work room for the other 145.5 hours. Applying only the space share would claim a fifth of the electricity for a room in use an eighth of the time. Most tax authorities that allow apportionment expect both factors, and the ones that do not usually publish a flat rate instead.
The choice of denominator is a judgement. 168 hours is the whole week and gives the most conservative figure. A waking-hours denominator of around 112 is defensible for costs like heating and lighting that nobody consumes while asleep. Whichever you choose, the page shows it, so the basis of the claim is on the face of the summary.
Limitations: what the result does not prove
- It is not tax advice and contains no tax rules. Deductibility, flat rates, employee versus self-employed treatment and the consequences of claiming a share of rent or mortgage interest are all country-specific.
- It cannot verify your bills, your floor area or your hours. The claim is only as good as the figures you enter, and a claim should be supported by the bills themselves.
- Claiming a portion of a property as business use can have other effects - on capital gains relief, on business rates, on a tenancy agreement or on home insurance. Those are outside what an apportionment calculator can see.
- The flat-rate comparison uses the rate you type in. No published rate is included, because they change and differ by country.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
Frequently asked questions
How do I calculate the business share of my electricity bill?
Take the bill as a monthly figure, multiply by the share of your home used for work (rooms or floor area), then by the share of the week you actually work there. One room of five used 22.5 hours a week gives 0.2 x 22.5/168 = 2.68% of the bill.
Should I use the number of rooms or the floor area?
Rooms are simpler and usually accepted; area is fairer when the work space is much larger or smaller than an average room. Use one method for the entire claim and note which one - mixing them line by line is what makes a claim look constructed.
Do I have to apply an hours factor as well as a space factor?
If the space has any private use, yes - otherwise you are claiming a fifth of the bill for a room in use an eighth of the time. Only choose "no time share" when the room is genuinely used for nothing else, and expect to be able to show that.
Is a flat rate better than apportioning?
Often, for part-time home workers with modest bills, because a flat rate requires no records. Apportioning usually wins when a large share of the home is used, when bills are high, or when there are wholly business costs. Enter the published flat rate and the page shows both totals side by side.
Can I claim a share of my rent or mortgage?
That depends entirely on where you live and whether you are employed or self-employed. Many countries allow a share of rent for the self-employed and almost none allow mortgage capital repayments. This page will apportion the figure if you enter it, but whether it is claimable is a question for your tax authority.
What counts as a room?
Conventionally, habitable rooms - bedrooms, living rooms, kitchen, study - and not hallways, bathrooms, landings or storage. There is no universal definition, so state your count and be consistent; a claim that quietly excludes rooms to raise the share is the first thing an inspector recalculates.
Does anything I type here get uploaded?
No. The apportionment runs entirely in your browser and no bill, address or figure is sent anywhere. Nothing is stored between visits either, so keep the CSV if you need a record.
Last reviewed by the A2Z.Tools team against the sources listed above.
