To obtain a deduction, the employee has to make a claim to the
Commissioners of HMRC. The procedure provided by Section 42 and
Section 43 TMA 1970 for making claims and resolving disputes
applies (see RE10 onwards).
In practice deductions can be allowed for an employee's
contributions to an overseas pension scheme provided you observe
the guidance at
EIM32671.
The power given to the Commissioners of HMRC by Section 355 is discretionary.