Proof of income is now required from some beneficiaries wanting to use legal aid money to fight court cases.
The change was brought into effect this week by the Legal Services Agency.
Those seeking legal aid for family and civil cases must now provide proof that they receive regular Work and Income assistance.
A letter from WINZ, or a bank statement showing transactions, are both deemed acceptable verification.
Domestic violence and cases considered urgent are exempted from the change, as are those in Christchurch for now.
The Law Society says under the old rules, a large number of applicants were falsely registering as beneficiaries.
The legal aid system is undergoing a major overhaul following a report in 2009, which found extensive loopholes in the system.
The Government is expected to announce further legal aid reforms next month.