(1)A deduction is allowed from earnings which are taxable earnings under section 15 or 21 (earnings for year when employee resident and ordinarily resident in UK) if—
(a)the earnings include an amount in respect of—
(i)the provision of travel facilities for a journey made by the employee, or
(ii)the reimbursement of expenses incurred by the employee on such a journey, and
(b)the circumstances fall within Case A, B or C.
(2)The deduction is equal to the included amount.
(3)Case A is where—
(a)the employee is absent from the United Kingdom wholly and exclusively for the purpose of performing the duties of one or more employments,
(b)the duties concerned can only be performed outside the United Kingdom, and
(c)the journey is—
(i)a journey from a place outside the United Kingdom where such duties are performed to a place in the United Kingdom, or
(ii)a return journey following such a journey.
(4)Case B is where—
(a)the duties of the employment are performed partly outside the United Kingdom,
(b)those duties are not performed on a vessel,
(c)the journey is between a place in the United Kingdom and a place outside the United Kingdom where duties of the employment are performed,
(d)the duties performed outside the United Kingdom can only be performed there, and
(e)the journey is made wholly and exclusively for the purpose of performing them or returning after performing them.
(5)Case C is where—
(a)the duties of the employment are performed partly outside the United Kingdom,
(b)those duties are performed on a vessel,
(c)the journey is between a place in the United Kingdom and a place outside the United Kingdom where duties of the employment are performed,
(d)the duties performed outside the United Kingdom can only be performed there, and
(e)the journey is made wholly and exclusively for the purpose of performing those duties, or those duties and other duties of the employment, or returning after performing them.