Can I claim my business phone calls and line rental as an expense?

Yes — business-related phone costs are allowable, but the approach depends on whether it's a personal or dedicated business phone. Dedicated business line: claim 100% of the line rental, calls, and contract costs. Personal phone with business use: only the business-use proportion is allowable. Estimate the percentage of calls and data used for business, and apply that percentage to your total bill. Keep your monthly bills. For contract phones: claim the business % of the monthly contract fee. If your employer pays for a phone and you use it privately, different rules apply. For sole traders using a personal mobile, 50% is a common and HMRC-accepted starting point if you genuinely use the phone roughly 50:50. Adjust up or down based on your actual usage.

• Dedicated business line: 100% of all costs are deductible
• Personal phone: claim only the business-use proportion of monthly bills
• 50% is a common starting point for dual-use phones — adjust to reflect actual use
• Keep phone bills as evidence of the split
• Claim under 'Phone, fax and stationery' on your SA103 return