13.—(1) In the circumstances prescribed by paragraph (2) a claim for a tax credit made by one member of a married couple or an unmarried couple is to be treated as also made by the other member of the married couple or unmarried couple.
(2) The circumstances prescribed by this paragraph are those where one member of a married couple or an unmarried couple is treated by regulation 12 as having made a claim for a tax credit in response to a notice under section 17 of the Act given to both members of the couple.