Know How Non Profit (an offshoot of NCVO) provides various guidance to ensure your organisation stays within the law.
Their website covers:
Charity law: The legal obligations of charities under the Charities Acts and the Companies Acts.
Governing documents: The key legal document in a charitable organisation is its governing document.
Policies and procedures: The set of policies and procedures that define, regulate and inform how you and your organisation operates.
Keeping records: Records that your non profit organisation must keep as evidence for compliance and checks.
A checklist for compliance: As a nonprofit organisation, make sure you know about the legislation that applies to you.
For more on legal requirements, take a look at the Know How Non Profit Governance section.