Deductions for expenditure incurred on the replacement of tractor units and trailers used in the trade were not allowable under the ‘replacement and alteration of tools’ provisions, and an overpayment relief claim was not permitted under the ‘practice generally prevailing’ exception. 
 
Summary

Deductions for expenditure incurred on the replacement of tractor units and trailers used in the trade were not allowable under the ‘replacement and alteration of tools’ provisions, and an overpayment relief claim was not permitted due to the ‘practice generally prevailing’ exception. 

Background

The appellant company carried on a road haulage trade. In the years 2008, 2009, 2010, and 2011 it purchased trailer units, tractors, and tank units for