📊 Annual Household Expenses
ℹ️ Enter Your Total Annual Bills
These are your total household expenses for the entire year. The calculator will apportion them based on business use.
➕ Additional Expenses (Optional)
💡 Common Additional Expenses
Mortgage Interest (not capital repayment), Rent, Repairs & Maintenance, Cleaning, Internet/Phone, etc.
Note: Choose apportionment type carefully - Fixed costs use space only, Variable costs use space × time.
🚪 Room Details
⚠️ Important: Business Use
Only claim rooms with genuine, regular business use. HMRC expects claims to be reasonable and evidence-based.
📘 How the Calculator Works
Calculation Methodology (ACCA Guidance)
Fixed Costs (Space-Based Only)
These expenses are payable whether rooms are occupied or not:
- Council Tax = Annual amount × (Room area % of total)
- Home Insurance = Annual amount × (Room area % of total)
Variable Costs (Space AND Time-Based)
These expenses are incurred only when rooms are used:
- Electricity = Annual amount × (Room area %) × (Time usage %)
- Gas = Annual amount × (Room area %) × (Time usage %)
- Water (metered) = Annual amount × (Room area %) × (Time usage %)
Additional Expenses
Fixed Additional Costs (Space-Based)
Apportion by space percentage only:
- Mortgage Interest (not capital) - payable whether occupied or not
- Rent - if you rent your property
- Ground Rent / Service Charges
Variable Additional Costs (Space × Time)
Apportion by both space AND time usage:
- Internet/Broadband - used when working
- Telephone Line Rental
- Repairs & Maintenance - general property repairs
- Cleaning - if paid for professionally
HMRC Simplified Method
For those who prefer simpler record-keeping, HMRC offers flat-rate deductions:
| Monthly Hours | Rate per Month | Annual Deduction |
|---|---|---|
| 25-50 hours | £10 | £120 |
| 51-100 hours | £18 | £216 |
| 101+ hours | £26 | £312 |
✅ Why Use the Detailed Method?
The detailed calculation typically saves 10-20 times more than the simplified method if you work substantial hours from home!
What Records to Keep
- ✓ All utility bills for 12 months
- ✓ Council tax and insurance documents
- ✓ Floor plans with measurements
- ✓ Business diary showing hours worked
- ✓ Photos of workspace setup
- ✓ Client meeting records (if applicable)
📝 Example Scenarios
Example 1: Dedicated Home Office
Situation: Sarah has a dedicated office room (150 sqft) in her 1,500 sqft home. She works 40 hours per week exclusively in this room.
Calculation:
- Space percentage: 150 ÷ 1,500 = 10%
- Time percentage: 100% (dedicated use)
- Council Tax: £2,000 × 10% = £200
- Electricity: £1,000 × 10% × 100% = £100
- Total allowable: ~£500/year
Example 2: Shared Dining Room
Situation: John uses his dining room (200 sqft of 2,000 sqft home) for business 30 hours/week, personal use 10 hours/week.
Calculation:
- Space percentage: 200 ÷ 2,000 = 10%
- Time percentage: 30 ÷ 168 = 17.9%
- Council Tax: £2,000 × 10% = £200 (space only)
- Electricity: £1,000 × 10% × 17.9% = £17.90
- Total allowable: ~£400/year
Example 3: Multiple Rooms
Situation: Emma uses: Office (100%), Kitchen (occasional calls), Bathroom (meets clients)
Approach: Calculate each room separately and sum the totals. Be conservative with shared spaces to avoid HMRC challenges.
Example 4: With Mortgage Interest
Situation: David has a dedicated 200 sqft office (10% of 2,000 sqft home), works 40 hrs/week. Annual mortgage interest: £8,000
Calculation:
- Mortgage Interest: £8,000 × 10% = £800 (space only - fixed cost)
- Plus standard expenses (Council Tax, Utilities, Insurance)
- Total additional allowance from mortgage: £800/year
- Important: Only mortgage INTEREST is allowable, not capital repayments
Note: If claiming significant business use of your home, this may affect Capital Gains Tax when you sell. Seek professional advice.
Common Mistakes to Avoid
❌ Don't Do This:
- Claiming 100% when rooms have personal use
- Not keeping supporting records
- Excessive or unreasonable claims
- Forgetting to apportion utilities by time
- Claiming non-metered water
- Claiming mortgage capital (only interest allowed)
⚖️ Disclaimer & Legal
This calculator is a tool to help estimate allowable expenses based on ACCA guidance and HMRC requirements. It does not constitute professional tax advice. Individual circumstances vary, and you should keep accurate records, consult with a qualified accountant, and review calculations with HMRC if uncertain.
References:
- ACCA - Allowable expenses when using home as office
- HMRC Business Income Manual BIM47825
- Income Tax (Trading and Other Income) Act 2005, Section 34