New tax rules announced today will stop high income earners claiming Working for Families and Student Allowances.

The definition of income for Working for Families, Student Allowances and Community Services Cards would be changed to prevent people structuring their income to increase their entitlements and shareholders would no longer be able to use loss attributing qualifying companies (LAQCs) to claim losses against their personal income.

The changes were expected to reduce spending on Working for Families by $32 million a year and make the tax system fairer, Finance Minister Bill English said.

''These changes will reduce the opportunities for well-off people to structure their affairs for tax purposes,'' he said.

The changes would be included in the Taxation (GST and Remedial Matters) Bill currently before Parliament and were likely to be debated on Thursday.

Revenue Minister Peter Dunne said changes to Working for Families and Community Service Cards would come into effect on April 1.

''The broader definition of income for social assistance will include income from family trusts, some fringe benefits in certain circumstances, income from a cash PIE that is not locked in and income from a spouse living overseas.''

Changes to LAQCs would ensure people could not claim tax deduction losses at a higher rate than they paid on profits, Mr Dunne said.