Possible Clues:

• Looking back, zero tax from firm - that's one for the books!
• Common choir music book size
• With eight leaves to the sheet
• Book or paper size
• A lot of notes presented by old book
• Old court bible, originally only this size?
• Form bookmaker used upset old tax company
• 6x9-inch book
• Size of book page made by folding each printed sheet into eight leaves
• Book page size — a CV too (anag)