MANY CORPORATE TAX-AVOIDANCE strategies are crafted with the help of the "big four" accounting firms - Deloitte, Ernst & Young, KPMG and PwC. These firms also happen to be among the longest-standing and best-represented providers of corporate services in offshore locations. Though they have a hand in designing bold avoidance schemes, the real problem is their acquiescence, says a former senior partner of one of the four. "Often the client would work with its lawyers to ensure the legal opinion was favourable and then present it to us as pretty much a fait accompli," he says. We were always on the defensive, being pushed to the limit. But to challenge them in that setting you had to have a particularly strong conviction that it was egregious. The big four see the furore over transfer pricing - manipulating intra-company transactions to shift profits to low-tax jurisdictions - as a growing reputational and legal risk. Big enough already, in fact, for them to hope that multinationals will in future think twice before asking their accountants to sign off on cheeky avoidance strategies, says the former partner. Loth to be seen as disloyal to their largest clients in public, the big four continue to lobby against changes in accounting rules that would make dodgy transfer pricing harder, such as country-by-country reporting. Privately, however, some of them see merit in such proposals and believe their adoption could help to reduce pressure on the profession. Tax activists are convinced the accountants want to maintain the status quo because complex tax-planning work is so lucrative. But accounting changes would bring new lines of revenue. If companies were to adopt country-by-country reporting, for instance, their auditors would have to sign off on more detailed sets of numbers, so their overall income would be unlikely to suffer much. That is why, ultimately, the big four won't lose much sleep over the current tax-avoidance kerfuffle, says another accountant.