The Australian Taxation Office wants to allow big business to oversee its own tax returns, internal documents reveal, despite the potential for conflict of interest, greed and even corruption.

The Tax Office has been working on a "transformational" plan to fundamentally change Australia's corporate tax system with companies allowed to use their own accountants to sign off on their tax bills, effectively outsourcing tax oversight to the private sector.

Illustration: Cathy Wilcox

But discussion papers obtained by Fairfax Media concede the plan, which will bring huge savings for the ATO, comes with dangers of conflicts of interest, greed or even intimidation corrupting the process.

The cash-strapped ATO, which plans to shed 900 jobs in the next six months, has been working behind the scenes for about 18 months on the scheme, which would be open to companies with annual turnover of between $100 million and $5 billion.