Possible Clues:

• In which a number of months are accounted for
• Important period for a CPA (2 words)
• A fancy airline (anag) — 12 months in the life of the Chancellor of the Exchequer
• What starts on April 6
• Period beginning in early April
• Accounting period
• 'Cranefly', in a first-class condition, goes from 6/4 to 5/4
• Accounting or tax period, eg 6 April - 5 April
• April 6 to April 5 for most of us
• April six to April five