Working from Home: HMRC Rules on Expensing Home Office Costs

More UK small business owners than ever are working from home, but the rules around expensing home office costs are anything but straightforward. HMRC has strict guidelines about what you can and can’t claim, and getting it wrong could mean missed opportunities or a painful tax bill. This definitive guide breaks down exactly how home office expenses work, what’s allowable for sole traders and limited companies, how to calculate your claim, and the pitfalls to avoid. Read on to make sure you claim every penny you’re entitled to—without falling foul of the taxman.

HMRC recognises that many small business owners work from home, but it’s not a free-for-all when it comes to expensing costs. The fundamental principle is that you can only claim expenses that are 'wholly and exclusively' for business use. This means any personal element must be excluded or apportioned correctly. The rules differ depending on whether you’re a sole trader, partnership, or running a limited company, and it’s crucial to get this distinction right from the outset.

For sole traders and partnerships (where all partners work from home), the rules are relatively flexible. HMRC allows claims for a proportion of household running costs, but you need a reasonable method to work out what’s business-related. For limited company directors, things get more complicated: you’re technically an employee of your company, and the rules about employee homeworking expenses apply. Confusingly, the 'wholly and exclusively' test interacts with other rules about employment benefits and the potential for personal use, so care is vital.

It’s also important to understand that HMRC scrutinises these claims. While small, reasonable claims rarely trigger an enquiry, large or poorly supported expenses can attract attention. Documentation, clear calculations, and a conservative approach are your best defences. HMRC’s own guidance is spread across several manuals and web pages, but this article brings it all together for small business owners.

Allowable expenses are those you incur in running your business from home. This can include a portion of your electricity, gas, water, council tax, rent, mortgage interest (but not capital repayments), broadband, and phone costs. However, you can only claim the part that relates to your business activities—anything used for personal purposes must be excluded. If you have a room set aside exclusively for work, you’ll typically apportion these costs based on the number of rooms and time spent working.

You can’t claim for things you would pay for anyway, such as general home repairs (unless directly related to your work area) or improvements that benefit the whole property. Capital costs (e.g., buying the property, extending your home) are also not allowable under running costs, though capital allowances may apply in very limited circumstances (equipment, not premises). Internet and phone bills can be claimed in proportion to business use—keeping an itemised record for a representative period is recommended.

For limited company directors, there’s a distinction between 'incurred expenses' (which the company can reimburse tax-free if certain conditions are met) and 'use of home as office' arrangements, which may require a formal rental agreement to avoid benefit-in-kind tax charges. It’s essential to keep business and personal costs clearly separated, with robust evidence to support your calculations.

If you’re a sole trader, you have two main options for claiming home office expenses: the actual costs method, or the simplified flat rate method. Each has pros and cons, and the right choice depends on your circumstances. The actual costs method lets you claim a proportion of your real household expenses. You’ll need to work out a fair way to apportion costs—typically by the number of rooms used for business, the time spent working, or a combination of both. For example, if you have five rooms and use one as an office for half the week, you’d claim 1/5 x 0.5 of your total eligible costs.

The simplified expenses method is only available to sole traders and partnerships with no corporate partners. It lets you claim a fixed monthly amount based on the number of hours you work at home each month, regardless of your actual costs. For the 2026/27 tax year, the rates are: £10/month for 25–50 hours; £18/month for 51–100 hours; £26/month for 101+ hours. This method is easier and reduces admin, but may result in a lower claim if your real costs are higher.

Whichever method you use, you must keep records to support your claim. For actual costs, this means utility bills, council tax statements, mortgage interest certificates, and a written explanation of your calculation method. For the flat rate, you’ll need a log of your working hours. Don’t forget that certain expenses (e.g., phone, broadband) can still be claimed separately for the business-use portion, even if you use the flat rate for other costs.

• Actual costs: Proportion of real household bills. Needs careful calculation.
• Flat rate: HMRC’s simplified expenses, based on hours worked at home.
• Phone/internet: Claim business portion separately—even if using the flat rate.
• Keep all records: Receipts, bills, working time logs.
• Watch dual use: Only claim the business part, not personal use.

Directors of small limited companies face a different set of HMRC rules. You cannot simply claim a share of your home running costs through your company in the same way as a sole trader. Instead, there are two main ways to claim home office expenses: the flat rate homeworking allowance, and a formal rental agreement between you and your company.

The flat rate method is straightforward: your company can pay you up to £6 per week (£26 per month) tax-free for working from home, with no need for receipts or detailed calculations. This covers additional household costs (heat, light, electricity) incurred by working from home. If you want to claim more than this, you must enter into a written rental agreement with your company, setting out the terms, amount, and what’s included. The rent must be reasonable, reflect market rates, and only cover genuine business use—otherwise, you risk a benefit-in-kind tax charge or invalidating your mortgage or home insurance.

Additional expenses such as broadband, business phone calls, and dedicated office equipment can be claimed by the company if used wholly for business and backed by receipts. However, you must be careful not to claim for costs that have a dual personal use, as this could trigger additional tax liabilities. Always seek advice before setting up a rental agreement, as there are legal and tax implications to consider.

• £6/week (£26/month) flat rate: No paperwork needed for this HMRC allowance.
• Formal rental agreement required for higher claims—must be at market rate.
• Company can reimburse you for business-only phone, broadband, and equipment.
• Risk of benefit-in-kind charges if claims are excessive or personal use is included.
• Rental income may need to be declared on your Self Assessment tax return.

The calculation of allowable home office costs is one of the trickiest areas for small business owners. The goal is to arrive at a reasonable, evidence-based figure that reflects the actual business use of your home. For most, this means apportioning costs by a logical method: typically by the number of rooms in your property, the percentage of time a room is used for work, and the proportion of bills that relate to the space.

For example, if your home has six rooms (excluding bathrooms and hallways) and you use one as an office for 40 hours per week (in a 168-hour week), you’d claim 1/6 of your eligible costs, further reduced by the percentage of time the room is used for business. It’s crucial to exclude any rooms that double as living space (e.g., a guest bedroom used for work only part-time), unless you can clearly demonstrate exclusive business use during working hours. HMRC expects you to use a consistent, reasonable approach year-on-year, and to keep detailed notes of your calculations.

For limited companies, if you’re paying yourself rent, the company can deduct the rent as a business expense, but you must declare this income on your personal tax return. If you’re claiming the flat rate, simply record the payments and ensure you don’t double up by also claiming a share of running costs. Professional advice is recommended for more complex situations (e.g., if you have a dedicated outbuilding or use a significant part of your home for business).

Many small business owners either under-claim, missing out on legitimate tax savings, or over-claim, risking penalties and a stressful HMRC investigation. Common mistakes include using the wrong calculation method (e.g., limited company directors claiming like sole traders), failing to keep records, or claiming for costs that are not exclusively business-related. Another trap is claiming for capital costs (e.g., property improvements or furniture) as running expenses, which HMRC will disallow unless capital allowances are available.

One of the biggest risks is triggering a benefit-in-kind charge for limited company directors. If your company pays you more than the flat rate or covers costs that have a personal element without a proper arrangement, HMRC can treat the payment as a taxable benefit. This means extra tax and NI for both you and your company. Likewise, entering into a formal rental agreement without informing your mortgage lender or insurer can breach your contract and risk invalidating your cover.

To avoid these pitfalls, always document your calculations, keep receipts and contracts, and use a conservative, logical approach. If in doubt, seek advice from a qualified accountant or tax adviser who understands HMRC’s latest guidance. HMRC is less likely to challenge claims that are clearly supported and fall within normal parameters for your business size and sector.

• Claiming for non-business use rooms or time
• No supporting evidence for apportionment method
• Directors using sole trader rules—wrong method
• Including capital improvements as running costs
• Not declaring rental income on Self Assessment

Good record-keeping is your best defence if HMRC ever asks about your home office expenses. This means keeping copies of all relevant bills, bank statements, contracts (including any rental agreement with your company), time logs, and a clear written note of your calculation method. HMRC generally expects you to keep these records for at least six years after the end of the tax year in question.

For actual costs, you should archive copies of your utility bills, council tax statements, and any other paperwork showing the amounts you’ve paid. Annotate bills to highlight which portions are business-related. For the flat rate method, keep a simple diary or spreadsheet showing the hours you worked at home each month. If you’re a director with a rental agreement, keep the signed contract and proof of rent payments from the company to your personal account.

If you’re unlucky enough to face an HMRC enquiry, you’ll need to provide this evidence quickly. Being organised can turn a stressful situation into a routine check. If you can’t produce records, HMRC can disallow your claim and impose penalties. Modern cloud accounting systems (like Xero, QuickBooks, or FreeAgent) can help you keep digital records, but you must still keep scanned copies or originals of key documents.

• Utility bills and council tax statements
• Mortgage interest or rent agreements
• Time logs or diaries showing work hours
• Contracts for any formal rental arrangement
• Receipts for business equipment and supplies

Some situations add extra complexity to expensing home office costs. If you use a garden office, converted garage, or outbuilding for your business, you can claim a proportionate share of running costs, plus capital allowances for certain fixtures and fittings (not the structure itself). However, if the space is used exclusively and permanently for business, you risk losing private residence relief on Capital Gains Tax when you sell your home. It’s usually better to keep some personal use—e.g., occasional storage or hobby use—to avoid this.

If you share your home with others (e.g., family, flatmates), only claim the costs you personally incur and the space you actually use for work. If the bills are in someone else’s name, you must show how your share is calculated. For joint mortgages or tenancies, split the eligible costs before apportioning for business use.

For VAT-registered businesses, you can reclaim the VAT element of business-use costs, provided you have valid VAT invoices. The apportionment rules are the same: only claim the business part, and exclude any personal use. Special rules apply to claiming VAT on home office equipment and outbuildings—seek advice for large claims or one-off purchases.