UK Self-Employed Allowable Expenses Master Guide 2026/27

Section 34 ITTOIA 2005: expenses must be "wholly and exclusively" for trade purposes. Strict test - no dual purpose. Examples PASS: (1) Trade-only tools / equipment: £400 industrial drill for self-employed builder. (2) Business-only software: Xero subscription. (3) Trade-specific clothing: hi-vis, work overalls with logo. (4) Client business meal: at restaurant, sole purpose discussion. Examples FAIL: (a) Personal clothing (even worn at work): suit, casual office wear. (b) Family meal "for business": dual purpose disqualifies entirely. (c) Holiday with business "elements": dual purpose. (d) Childcare for working parents: domestic expense even if essential for trade. Apportionment for genuinely shared use: (1) Vehicle 60% business / 40% personal: deduct 60% of running costs. (2) Phone 80% business: deduct 80%. (3) Home office: see simplified or actual methods.

Revenue expenses: short-life consumed items. Full deduction in year of purchase. Capital expenses: long-life assets. Deduction via capital allowances over multiple years. Annual Investment Allowance (AIA) £1,000,000: full first-year deduction on qualifying plant + machinery. (1) Computers + IT equipment: AIA up to £1m. (2) Tools + equipment: AIA. (3) Vehicles - cars NOT in AIA: writing-down allowance 18% or 6% (high-emission). EVs / zero-emission cars: full first-year allowance (FYA). (4) Commercial vehicles (vans): AIA available. (5) Office furniture: AIA. Worked example - sole trader buys £2,000 laptop + £500 office chair + £15,000 van: All AIA eligible. Full deduction in year 1: £17,500 reduces trading profit. Tax saving (basic rate 20%): £3,500. Higher rate: £7,000.

2 methods: Method 1 - Simplified flat rate (HMRC simplified expenses): (a) 25-50 hours/month: £10/month = £120/year. (b) 51-100 hours: £18/month = £216/year. (c) 101+ hours: £26/month = £312/year. No receipts needed. Method 2 - Actual apportioned: (1) Identify dedicated workspace: e.g., spare bedroom 100% business. (2) Calculate proportion of home: % of floor area + hours. (3) Apply to expenses: heating, lighting, council tax, mortgage interest, broadband. Worked example - 1 room out of 5, used 9-5 weekdays: 20% floor area × 50/168 hours = 6% of bills. Annual heating £1,200 × 6%: £72. Electricity £600 × 6%: £36. Broadband £400 × 50%: £200 (business use proportion). Council tax £1,800 × 6%: £108. Total actual: ~£416. vs Simplified £312: actual marginally better but more admin. Choose annually: switch year-to-year. Capital gains warning: if room 100% business + you sell home, partial CGT applies to that proportion.

Method 1 - Simplified mileage: 45p / mile first 10,000 business miles + 25p / mile thereafter. No need to track actual costs. Covers fuel, insurance, MOT, servicing, depreciation. Method 2 - Actual + apportionment: (1) Total all vehicle costs: fuel, insurance, road tax, MOT, repairs, parking. (2) Mileage log: business vs personal miles. (3) Deduct business proportion. (4) Plus capital allowances on vehicle purchase: WDA 18% or 6%. Cars vs vans: (a) Cars: WDA only (NOT AIA). 18% pool for emission ≤50g/km. 6% pool for emission >50g/km. (b) Vans (commercial): AIA full deduction year 1. (c) Electric cars: FYA 100% year 1 deduction. Worked example - 15,000 business miles + 5,000 personal: Simplified: (10,000 × 45p) + (5,000 × 25p) = £4,500 + £1,250 = £5,750. Actual: £4,000 fuel + £600 insurance + £1,200 servicing + £200 MOT = £6,000 × 75% business = £4,500. PLUS WDA on car ~£800. Total £5,300. Simplified usually better unless high cost / low mileage.

Business travel deductible: (1) Client meetings: away from regular workplace. (2) Conference attendance: industry events. (3) Site visits: between workplaces. (4) Training courses: maintain trade skills. NOT deductible: (a) Home to regular workplace commute: ordinary commute, never deductible. (b) Personal travel: never. Subsistence: (1) Reasonable meals during business travel: deductible. (2) Hotel accommodation away from home: deductible. (3) Local meals at home base: NOT deductible (would also eat anyway). (4) Client entertainment - food + drink: NOT deductible (Section 56 ITTOIA 2005 specifically disallows). (5) Staff entertainment up to £150 / head / year: deductible. HMRC simplified meal rates (2026/27): (a) £5 if travel 5+ hours over normal mealtime. (b) £10 if 10+ hours. (c) £15 if 15+ hours. (d) £25 if late + overnight. Or claim actual: receipts required.

Deductible categories: (1) Trade-specific tools: hand tools, power tools, professional equipment. AIA up to £1m. (2) Office equipment: computer, printer, scanner, monitor, keyboard. AIA. (3) Software: (a) One-off purchases (perpetual license over £200): AIA / capital allowance. (b) Subscriptions: revenue deduction. (4) Mobile phone for business: (a) Sole business phone: 100% deductible. (b) Shared business / personal: business proportion. (5) Internet broadband: business proportion. (6) Cloud storage + SaaS: full deduction. (7) Trade subscriptions: industry-specific. (8) Professional development: training courses, CPD, certifications. (9) Tools maintenance: repairs, servicing, sharpening. (10) Safety equipment: PPE, safety boots, hi-vis - 100%. Strict purpose test: even tools "mostly business" must be apportioned if any personal use. iPhone 60% business / 40% personal = 60% deduction only.

Deductible professional fees: (1) Accountant fees: SA preparation, bookkeeping, advice. Including tax investigation defence. (2) Solicitor / legal fees: business-related (NOT divorce, will, criminal defence). (3) Business consultant fees: management consulting, marketing, design. (4) Industry memberships: HMRC List 3 approved bodies (ICAEW, ACCA, BMA, RIBA, RICS, etc.). (5) Trade union fees: separate but parallel. (6) Professional indemnity insurance: protection against client claims. (7) Public liability insurance. (8) Business buildings + contents insurance. (9) Specialist business insurance: e.g., cyber, key person. Tax investigation insurance: deductible. Bookkeeper / virtual assistant: fully deductible. NOT deductible: (a) Fines + penalties: HMRC, regulator, parking tickets. (b) Speeding tickets while business driving: still personal. (c) Bribes + corrupt payments: never deductible (Section 1304 CTA 2010 + ITTOIA equivalent).

Marketing fully deductible: (1) Google Ads / Facebook Ads: PPC + display campaigns. (2) SEO services: agency fees. (3) Email marketing platforms: Mailchimp, ConvertKit. (4) Print advertising: newspaper, magazine, flyers. (5) Business cards + stationery. (6) Signage: shop signs, vehicle wraps. (7) Trade show fees + exhibition stands. (8) Promotional gifts to clients ≤£50: small business gifts deductible. (9) Sponsorship: with genuine business benefit. Website costs: (1) Domain registration: revenue. (2) Hosting subscription: revenue. (3) Initial website build: (a) Display website: revenue if cheap (<£200) / capital if substantial (designed once + used many years - typically capital). (b) E-commerce / functional website: capital - integral to trading function. (4) Ongoing maintenance + updates: revenue. (5) Plugin / theme purchases: revenue or AIA. SEO + content creation: revenue.

Each tax year choose: (1) Vehicle: simplified mileage 45p/25p OR actual + capital allowance. (2) Home office: £10/£18/£26 monthly OR actual apportioned. (3) Premises live-in (e.g., B&B owner): simplified £350/£500/£650 monthly OR actual apportioned. Once chosen for vehicle: stick with vehicle simplified for that vehicle's lifetime in business (cannot switch back to actual later). Home + premises: can switch year-to-year. Strategic considerations: (1) Calculate both methods first year: choose larger deduction. (2) Annual review: situations change. (3) MTD ITSA from April 2026: digital records required regardless. Actual method needs more transaction tracking. (4) Specialist accountant valuable: identifies missed deductions. Common SE missed deductions: (a) Use of home actual costs: often higher than simplified £312. (b) Business mileage logging: many overestimate personal, underestimate business. (c) AIA on expensive equipment: full first-year not always claimed. (d) Professional subscriptions: forget to claim. (e) Training + CPD: often missed.

Pre-trading expenses: business setup costs before trading begins. Section 57 ITTOIA 2005: deductible IF: (1) Incurred within 7 years before trading start. (2) Would have been deductible if incurred during trading. (3) Same business that subsequently traded. Treated as Day 1 expense: reduces first year's profit. Common pre-trading expenses: (1) Market research. (2) Business plan preparation. (3) Initial training + qualifications: directly related to trade. (4) Legal + accounting fees for setup. (5) Equipment purchased pre-launch: AIA in first trading year. (6) Website + branding. (7) Domain + hosting setup. (8) Stock purchases pre-launch. (9) Office setup costs: rent deposit, decoration. (10) Insurance pre-trading period. Worked example - new freelancer spent £2,000 in 6 months before first invoice: Course £800 + laptop £900 + software £200 + marketing £100. All deductible. First-year tax saving (basic rate): £400. Don't forget to claim: easily overlooked.

Common items WRONGLY claimed as deductions: (1) Client entertainment food / drink: NOT deductible (Section 56 ITTOIA 2005). Includes restaurant meals, drinks bills. Staff entertainment up to £150 / head / year OK. (2) Personal clothing: even worn at work. Only branded uniform or essential PPE. (3) Childcare: even essential for parent to work. (4) Personal grooming / haircuts: even for client-facing roles. (5) Fines + penalties: parking, speeding, HMRC, regulator. (6) Personal life insurance: only key-person insurance for business. (7) Personal pension contributions: separate from business deduction, claim via SA personal section. (8) Capital expenditure on home (extensions, kitchens): not deductible for business even if work from home. (9) Bribes / corrupt payments: never. (10) Charitable donations: separate Gift Aid scheme, not business expense. (11) Spouse "wages" without genuine work + market rate: HMRC challenges. (12) "Mostly business" personal items: dual purpose disqualifies entirely (rare exceptions for genuine apportionment).

Self-employed expense optimisation: (1) Track every business expense daily: app or spreadsheet. (2) Keep receipts digital: photo + cloud storage. (3) Separate business bank account: simplifies tracking + auditing. (4) Mileage app: MileIQ, TripLog, Driversnote - GPS-based. (5) AIA up to £1m on equipment: full first-year deduction. (6) Pre-trading expense claim: 7 years backdated. (7) Annual simplified vs actual review: vehicle + home + premises. (8) Pension contributions: separate tax relief via personal SA. (9) Class 2 NI voluntary if profit < £6,725: builds State Pension. (10) Class 4 NI 8% / 2%: above £12,570. (11) MTD ITSA preparation April 2026: digital records + software (Xero, FreeAgent, QuickBooks). (12) Specialist accountant: £400-£1,500/year typical. Identifies overlooked deductions worth £k+. (13) Save 25-30% of profit monthly: tax reserve. (14) Payment on Account July + January: cash flow management. (15) Annual budget review: ahead of tax year end. (16) Spouse employment if genuine work: family tax efficiency. (17) Capital allowances on company vehicles + tools: maximise WDA / FYA / AIA. (18) Trading allowance £1,000 if very small income: optional simplified mode. (19) Tax investigation insurance £100-£300/year: protects against fees. (20) Record retention 5 years after SA filing: HMRC review window.