In an unusual set of circumstances, from Wednesday Mr Billson stepped in to fill Joe Hockey's shoes as the Treasurer, fresh from a partial victory in his defamation case against Fairfax Media, took two weeks holidays.

That leave coincides with Finance Minister Mathias Cormann leading a European-Australian Business Council delegation to Belgium, Germany and Italy where he will push for an EU-Australia free trade agreement, meet German Vice Chancellor Sigmar Gabriel and Federal Finance Minister Wolfgang Schauble, Belgian Minister for Finance Johan Van Overtveldt and the EU Trade Commissioner Cecilia Malmstrom.

Assistant Treasurer Josh Frydenberg is also on holiday.

Last year, after delivering a budget that was widely criticised for breaking a slew of promises and being unfair, Mr Hockey drew further criticism from his colleagues for taking a holiday in Fiji during a key parliamentary sitting.

But the second Abbott-Hockey budget has attracted nothing like the same opprobrium - and in fact, a good deal of praise from small businesses delighted with the 1.5 per cent tax cut, tax discounts for unincorporated businesses and generous $20,000 tax write offs.

And Mr Billson, whose zest for his portfolio is such that he has boasted that "even my blood group is positive", is taking the temporary promotion in his stride.

It has been, he tells Fairfax Media, 19 years in the making.

"I obviously enjoy the opportunity and am and have been engaged with the Treasury portfolio matters anyway - I'm a cabinet minister in the portfolio," he says.

"So it's a continuation of what I am doing as Small Business Minister anyway."

"It's pleasing to me in recent months that everyone has been talking about small business, though I've been talking about it for the last five years, since becoming spokesman."

On the challenges facing the Australian economy, Mr Billson says the federal government is closely monitoring the developments in Greece.

"I'm receiving daily reports about what is happening, fortunately our direct exposure to the Greek economy is relatively modest.  We have a strong and resilient banking sector, considerable strength in our economy and a credible plan to bring our own budget to surplus," he says.

"I am getting some extra briefings relating to important and current events like Greece, but in the ordinary course of how the economic team works, we ensure each member of the team is kept informed."

"I'm also able to access ministerial staff who ordinarily support the work of the minister, to the extent that anything has changed those offices operate as usual and I'm subbed in as the minister."

However, shadow treasurer Chris Bowen criticised the absence of the senior economic ministers.

"It's clearly not appropriate for a junior minister to be acting Treasurer and acting Finance Minister for the best part of two weeks. This is poor management by the government and the Prime Minister's office," Mr Bowen said.

"It wasn't too long ago that the Abbott government was screaming the house down claiming Australia was in danger of a Greek debt crisis, now, as soon as Greece defaults on its debt repayments and the consequential global uncertainty that flows from this, it's feet up from the Abbott government."

But Mr Billson fired back at Mr Bowen, lashing Labor's description of the small business portfolio as a "junior position, while the Coalition saw it as a valued senior post".

"Labor have always said they have never been a party for small business and a statement like this backs that up. Under Labor there was a revolving door of small business ministers with six in six years. Clearly with statements like this Labor don't understand the importance of small business to the economy or value the portfolio," he said.

Senator Cormann is due to return to Australia on July 11.

Until then, the man who has put small business on the political map will hold the reins.

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