Reason Bertie got artists’ tax exemption?

The reason Bertie got artists’ tax exemption, as explained in The Irish Times letters page the other day:

Bertie Ahern’s tax perk

Madam, – When I wrote a biography of Brendan Bracken I was denied the artists’ tax exemption by the Revenue because a biography, being a recital of facts, did not rank as an original and creative work. Are we to infer from their determination in relation to Mr Ahern’s memoirs that they are fiction? – Yours, etc,

Strand Road,
Dublin 4.