Reimbursement of telephone charges for calls made during the course of your employment would be a legitimate expense and would not attract taxation.
Reimbursement of private calls made from your own home telephone would be considered a benefit by HM Revenue and Customs and would be subject to their formula for calculating the appropriate 'cost of benefit', which then becomes a taxable item.
The provision of a mobile telephone is not regarded by HM Revenue and Customs as a taxable benefit.
The Regulations are complex and further advice can be sought from your local tax office.
