The wonderful thing about investigating multinational tax avoidance is that, despite the corporate spin and obfuscation, there is a hard number that you can always hang your hat on.

No matter the highfalutin excuses from slick PR types and the rhetoricians of the corporate tax lobby for why such paltry tax is paid; no matter the illimitable complexity of tax laws and financial engineering, this precious number displays how much tax has been paid to the Australian Tax Office each year – cash.

The claim against MasterCard would be the UK's biggest and one of the first filed under the Consumer Rights Act 2015. Credit:Jim Rice

It can be found in the cash-flow statement of a company's annual financial statements – unless the company has a special exemption from the regulator from having to disclose. Or unless the name of the company is Westfield Corporation, which bizarrely counterveils accounting standards by grouping income tax with withholding tax. And it can be found about six lines down from "operating cash-flow", and it usually says "tax paid".

So it is that once you have trawled the database, stumbled upon the relevant entity and paid ASIC the requisite fees, you will find, for instance, that global credit card giant MasterCard last paid $4.3 million in tax to the Tax Office. That was for the year to December 2014. This is lower than the year before, when it somehow got $429,650 back from the taxman, which is nice work if you can get it.