Once they had sought the blessing of the Office of Best Regulatory Practice that is. This was a sensible move, since the actual exemption deems Facebook Australia to be "a small Pty Company Controlled by a Foreign Company which is not part of a Large Group". It was always going to be hard for Thursday's hearings to live up to the sheer entertainment of Wednesday's spectacle when Apple, Google and Microsoft bosses were grilled about their fancy tax structures. But Wednesday's proceedings were by no means a let-down. The apparent risk of rich people being kidnapped as a result of tax disclosures sprang to life again when Treasury executive Rob Heferen was asked his view on whether compelling big private companies to lodge financial statement might carry a personal safety risk.

The government has foreshadowed that it might give 700 of the nation's biggest private companies an exemption from filing accounts because of kidnapping concerns and commercial confidentialities. Asked whether Treasury had provided advice to government on kidnapping, Heferen said he was aware of the debate but said that no advice had been offered by Treasury on kidnapping. Whether kidnappers will still be able to pore over ASIC Form 388 lodgements in order to evaluate their prospective targets, well, time will tell. The kidnap issue and the Facebook disclosures are part of a common theme at the tax inquiry: transparency. If you can't see it, you can't tax it.

Broadly, the tax and business lobbies and the Big Four accounting and audit firms have championed less disclosure, or the same opaque disclosure which is helping to run down Australia's corporate tax base. Consumer groups such as the Tax Justice Network and most people in the country with an opinion on the subject favour more disclosure. The Australian Taxation Office squibbed on the question yesterday, saying it was a matter for government. When asked by committee chair Sam Dastyari to disclose its No.1 multinational tax avoider under parliamentary privilege yesterday, ATO chairman Chris Jordan flatly refused. A barney ensued. It emerged that Jordan had sought advice from Treasurer Joe Hockey, who had endorsed his refusal to keep it secret. Tax shenanigans thrive on secrecy. Tax havens are also known as "secrecy jurisdictions" for a reason.

When Ernst & Young representatives appeared before the inquiry on Thursday they ducked for cover at the mention of Singapore. Perhaps because Singapore is the rising threat to Australia's tax base. It is a tax haven. It has very high levels of secrecy. All the Big Four accounting firms advise clients in Singapore and advise clients in Australia on how to order their tax affairs through Singapore. This is big business. Accordingly, the challenge of Singapore "marketing hubs" has come up time and again at the inquiry.

These are companies set up purportedly for marketing purposes but whose real use is to buy Australian products and services on the cheap before selling them at a higher price somewhere else. The effect is lower taxes paid in Australia and lower royalties. The ATO acknowledged it was a problem. Google acknowledged it booked the entire $2 billion-plus income from its Australian advertising customers through Singapore. Google's apparently Australian business, which sells advertisements to Australian customers in Australia, is corporately, Singaporean, and therefore presumably contributes to the roads, schools and hospitals in Singapore.

There's an estimated $60 billion plus of capital flowing out of Australia into tax havens annually. Most of this is in related party transactions whereby a company shifts money offshore where it attracts less tax. When asked if the Big Four, the same people who helped advise their clients secretly how to secrete money to secrecy destinations, had too cosy a relationship with Treasury and the Tax Office, Treasury's Heferen looked like he really wanted to keep it a secret And so he was also loathe to say who had provided advice to government on tax laws and policy, and what advice that was. That you see, was a secret. Yet despite the advice, the secondments and the revolving doors between government and the Big Four, Heferen balked at the idea that the relations between big business and government were "cosy". He wasn't alone. The very idea was a "conspiracy theory" Liberal senator Sean Edwards thundered at Greens' Senator Milne.

Audits, protested Heferen, were far from cosy, for example. "It's not actually all that cosy particularly when you get people from the Tax Office over, let me tell you," he said. Last week, the government unveiled its whitepaper on tax. "Re:think" it is called. "Everything is on the table," they said. Really? Everything, like negative gearing, super concessions, corporate trust structures, land tax, mining tax, carbon tax, family trusts?

The rub with tax is that people like other people to pay it and there is a stasis in reform. Vested interests thwart any significant change. But Tax Office is on a mission, it says. It has identified another $1 billion in extra corporate tax receipts by 2017, very little in light of the enormity of the revenue challenge we face. But real change is needed and the best place to start is secrecy. If there was greater transparency there would be higher tax receipts. Tax avoidance relies on secrecy.

The chicanery of some of the world's biggest tax dodgers is all over the airwaves this week. Surely they now realise that there is a reputational cost for their aggressive tax practices. There is an increasing public recognition of the scourge of tax avoidance. People are more concerned than ever with tax fairness. That's why, already, the Senate tax inquiry is a success.