(1) The Principal Act is hereby amended, in Chapter 2 of Part 18 -

(a) in section 530(1) -

(i) by the insertion of the following definition after the definition of "forestry operations":

"'income tax month' means a month beginning on the 6th day of any of the months of April to March in any year;",

(ii) by the substitution of the following for the definition of "qualifying period":

"'qualifying period' means the period of 3 years, or such shorter period as the inspector may allow, ending on the 5th day of April in the year preceding the year of assessment which is the first year of assessment of the period, in respect of which a certificate of authorisation is sought together with the period, if any, from the 6th day of April in the said first year of assessment to the date on which the application for the said certificate is received by the Revenue Commissioners;",

and

(iii) in the definition of "relevant contract" by the substitution of the following for paragraph (c):

"(c) to furnish the contractor's own labour or the labour of others in the carrying out of relevant operations or to arrange for the labour of others to be furnished for the carrying out of such operations,",

and

(b) in section 531 -