A draft Inland Revenue briefing supports lifting the GST rate if required - and notes tax credits could help people on lower incomes.

The IRD briefing also brought up the lack of a capital gains tax, but did not endorse any specific view on it.

Tax expert Geof Nightingale told Heather du Plessis-Allan that lifting GST is a fast and efficient way to raise revenue.

But he says while quick, it's much harder on lower-income people.