A tumultuous six years of declared debt and deficit crises, culture wars and internal warfare, the Coalition's sixth Budget seems to reflect a government that has collapsed, exhausted, in on itself.

There is some new spending and new tax cuts. But few new ideas.

When you are on a good thing, it seems, stick to it: extend some tax cuts you have already announced; extend an asset write off for small business.

Can the Coalition match Labor?

Equally, so many of the measures in the Budget reflect the reality of the Government's bleak political position: they are driven by a need to match Labor, or sandbag the Government against Labor policies.

All over the Budget are references to guaranteeing Medicare, to boosting apprenticeships.

And there is little left in the tin to spend during the election campaign according to the Budget papers: just $2.66 billion of decisions taken but not yet announced.

Labor will go into the election with a larger war chest. ( ABC News: Marco Catalano )

By comparison, Labor will wear the opprobrium of introducing increased taxes via policies like negative gearing and new capital gains tax arrangements, but go into the election campaign with a significantly larger war chest.

Built in to the Budget is the hope that voters will give the Government brownie points for cutting their taxes (almost immediately if you are a low to middle income earner) or believe a promise to cut tax rates more in 2022-23 or even 2024.

Despite all the rhetoric about good budget management, there are few big spending cuts, other than $2.1 billion over five years from forcing people receiving income support reporting any income they earn every fortnight.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 25 seconds 1 m 25 s Josh Frydenberg tells 7.30 host Leigh Sales that the budget will return to surplus in 2019-20. ( ABC News )

Budget surplus reflects NDIS cuts

There is little sign of fiscal restraint, and it is worth unpacking how the much trumpeted forecast return to surplus — $7.1 billion in 2019-20 — rests on a $3 billion underspend in the National Disability Insurance Scheme, after a $3.4 billion underspend in the current financial year.

According to the Budget papers, spending on the NDIS will be down from a forecast in last year's Budget of $16.7 billion in 2018-19 to $13.345 billion, a drop of $3.4 billion.

Around $1 billion of that will be as a result of reduced contributions from the state and territory governments.

Last night's Budget papers also show spending on the NDIS in 2019-20 will fall $3 billion, from the forecast in last year's Budget of $20.75 billion to $17.85 billion, and representing a total reduction in forecast spending on the NDIS over the two years of $6.5 billion.

The Federal contribution's spend on the NDIS within this total will be down $4.4 billion over the two years.

The Government insists that the underspend only boosts the surplus by $1.6 billion in 2019-20

There are a range of reasons for the underspend.

While some disability advocates say that a tightening up of definitions of conditions has seen people lose packages, the overwhelming problem remains that there are huge bottlenecks caused both by major problems in the NDIS' internal systems, and by problems in the supply of services at time when the disability services market is being transformed by the arrival of the NDIS.

Underspend or overspend? It's enough to make you dizzy

The Government says the NDIS is a demand-driven system and that the underspend is a result of the Federal Government overestimating the amount of people that would use NDIS services, based on State Government estimates.

"Not one cent will be cut from participants' NDIS plans as a result of the 2019-20 Budget — in fact plans will increase to account for an $850 million injection in 2019-20, announced recently, to grow the NDIS services market and increase the choices available for NDIS participants," Social Services Minister Paul Fletcher said.

"The NDIS is uncapped — every Australian with a disability who is eligible will continue to receive a fully funded plan of reasonable and necessary supports to achieve their goals, in accordance with the NDIS Act introduced with bipartisan support in 2013."

What if the government changes? In this environment of global unpredictability, the very idea of forecasting four years into the future feels bizarre. Even more so when we know this to be a document drafted with next month in mind, writes Annabel Crabb. Read more Read more

The Government argues, however, that at the same time it under-estimated how much would need to be spent on hospitals by exactly the same amount, because many potential NDIS clients simply used the hospital system.

It says money is, as a result, basically being transferred from the underspend on NDIS ($1.6 billion) to the overspend on hospitals ($1.9 billion).

The Government is also benefitting from a $1.9 billion improvement in non-tax receipts in the current 2018-19 year, which the Budget papers says reflect upward revisions in Future Fund Earnings.

Why does what happens in 2018-19 help the Government reach a surplus in 2019-20? Because the Government has actually included $2.8 billion of the policy decisions it announced on Tuesday night in the 2018-19 Budget, and as a result, reducing the amount of spending in the Budget bottom line next financial year.

In fact, new spending in 2019-20 is just under half the new spending put in the current year's Budget at $1.5 billion.

Can we trust the figures?

Underlying all the figures is an economic picture which is not exactly wildly reassuring.

Risks abound domestically and offshore.

Growth forecasts have been cut back.

The impact on the Budget bottom line is that the Government has been able to construct its story of economic rectitude on the back of a short term surge in company tax collections as a result of higher commodity prices.

But beyond that, the forecasts are for other tax collections to fall.

In bad news for state governments, this is particularly true of the GST — which is passed on to the states.

The Budget says that weaker household consumption and housing investment is behind these weaker GST collections.

There will be $10.3 billion less GST collected over the next four years than previously thought, and the states will be receiving $8 billion.

Laura Tingle is 7.30's chief political correspondent.