Ordinary Commuting - Duties defined by reference to a geographical area

I am a regional manager working within a geographical area, visiting sites and customers, the visits to the sites and customers I visit within the geographical area are random with no regular pattern to the visits - they are not permanent workplaces. I have an office outside of the geographical area which is between my home and the edge of the geographical area I manage, which I visit once a week, as the office is defined as a permanent place of work, I do not claim tax relief on those journey's. When I am visiting the sites and customers within the geographical area what level of tax relief should I be claiming, is it permissible to claim from home to the sites and customers visited which are not permenent workplaces?

Hi,

Have a look at EIM32202 below.

EIM32202 - Travel expenses: travel for necessary attendance: duties defined by reference to a particular area 

This is an example advising what travel is allowable. As an employee, you would use the approved mileage allowance if using your own vehicle for work.  

There is guidance on using your own vehicle at EIM31205.

EIM31205 - Employees using own vehicles for work

Thank you.