Home Office Deduction Calculator
How much of a household bill a home workspace can claim, by area.
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Formula
How the calculation works
A home workspace does not cost extra; it takes a share of a bill you already pay. The share is the workspace's floor area against the home's, and it applies to rent and utilities alike. On the example, 120 of 1,200 is a tenth, so 3,000 of the 30,000 rent and 500 of the 5,000 utilities.
Adding those shares over twelve months gives 42,000, which is the figure a tax return can claim as a business cost. It is not money in hand -- it is an expense the tax office will recognise.
Common mistakes
- Counting the workspace's whole area including shared space. Only the part used for work can be claimed, so a corner of a room counts as its portion, not the room.
- Treating the deduction as a saving. The bills were paid either way; the benefit is a smaller taxable profit, not a smaller bill.
When to use it
- Use it before filing, when the workspace is a fixed part of the home and its size is known, to put a defensible figure on the claim.
- It splits by area only. A workspace with its own meter, or one used partly for private things, needs a different rule this tool does not model.
Worked example
Rent 30,000 and utilities 5,000 with an area of 120 of 1,200: 3,000 of rent, 500 of utilities, 42,000 a year to claim.
Common questions
Is this a saving?
No, it is an expense figure -- you already paid the bill. But the share can be claimed as a business cost against income tax.
Which area do I use?
Use the work room's own size and the whole home's size. If the workspace is not a separate room, use its portion.
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