Not compulsory, but the trustee (ultimate person responsible for making decisions surrounding the activities of the trust) is 'legally' required to ensure adequate accounting records are kept (note legal and tax requirements are a different thing - hence the quotation marks). So in the event there was a mistake in accounting/tax treatment, a beneficiary (person who is entitled to income or capital of the trust) might want to sue, and the trustee would be personally liable for any mistakes because they didn't uphold what's called a fiduciary duty (in laymans terms you let everyone down by not doing your job of looking after the trust assets properly). That's all worst case scenario though. Funnily enough families tend to squabble quite a bit and that happens more that you'd think.
