They should also include help for 3.2 million Australians on low and modest incomes who are disadvantaged by the super system.

Next Tuesday's budget will put in place measures that go further in hitting the better off than those proposed by Labor.

Those who earn more than $300,000 now pay 30 per cent in super contributions tax compared with 15 per cent for everyone else.

The Turnbull government will lower the $300,000 income threshold to $180,000. Labor's policy is to lower the threshold to $250,000.

Higher earners will still get a tax break of 15 percentage points on their pre-tax super contributions, since the top marginal tax rate is 45c in the dollar.

But the big question is whether the Turnbull government will stick with the stated Coalition policy of ending the low-income superannuation contribution (LISC) from July 1, 2017.

Under the LISC, those on the lowest incomes receive up to $500 a year into their super accounts as a co-contribution from the government.

Labor introduced the LISC in 2012 as compensation for the fact that lower earners pay less than 15 per cent tax on their income, yet pay contributions tax of 15 per cent on their compulsory super and any voluntary contributions.

All other workers receive an effective tax break on their compulsory super and any salary sacrifice contributions because they pay more than 15 per cent in income tax.

It would be only fair that some of the savings made by lowering the threshold for higher earners be put towards covering the cost of continuing to pay the LISC.

The budget could free up even more money by lowering of the caps on how much can be salary sacrificed in super each year.

This cap is $30,000 for under-50s, and $35,000 for those over 50, and includes the 9.5 per cent superannuation guarantee.

Most people never get close to salary sacrificing up to the caps. It is only higher earners who can take full advantage of them.

Someone earning $180,000 a year receives a super guarantee $17,100.

If they are under 50, the annual limit is $30,000 and they can sacrifice up to almost $13,000 into super.

If the cap for under-50s was lowered in the budget to say, $25,000, the same person could only sacrifice up to $7900.

You can see how a lowering of the salary sacrifice caps would make a big dent in the value of tax concessions going to higher earners that could be better targeted elsewhere.

In its pre-budget submission the Association of Superannuation Funds of Australia called for the LISC to be retained.

"The single most effective, equitable and targeted measure to address the issue of people with low incomes is the LISC," the association's submission says.

Surely, more than enough savings in tax breaks going to the top end could be found to pay for the indefinite retention of the LISC.

If the Turnbull government is fair dinkum about fairness that is what it will do.

Twitter: @jcollett_money