In a court case starting today, the US Internal Revenue Service is facing off with the Bank of New York Mellon (BNY) over whether or not controversial tax planning measures that were designed by Barclays are legal.

The IRS claims that cross-border deals that Barclays prepared for the bank, as well as several other mid-sized ones like it, were in fact tax evasion, designed to exploit loopholes that exist in the difference between British and American laws.

The deal designed by Barclays is known as "structured trust advantaged repackaged securities" – STARS, for short – and it really is Byzantine [2]:

Barclays required Petitioner [BNY] to transfer assets that produced income to a trust that would have a U.K. trustee so that the U.K. trustee, as a U.K. resident, would owe and pay U.K. income tax on that income. Of course, from Petitioner's perspective, Petitioner wanted a favorable borrowing rate but did not want to pay taxes twice on the same income. As between the U.S. and the U.K., Petitioner was neutral as to whom it paid its income tax; it just wanted to avoid being double-taxed.

That's BNY's description of the STARS deal. The IRS's is marginally simpler, and significantly more damning:

A U.S. taxpayer who pays $1 of foreign tax and claims $1 of foreign tax credit pays the same amount of tax as if it had paid the $1 to the United States. A U.S. taxpayer who pays $1 of foreign tax, is reimbursed for 50 cents of it by a counterparty, but still claims $1 of U.S. foreign tax credit comes out ahead by 50 cents.

If the counterparty simultaneously recovers the $1 of foreign tax through the foreign tax system, uses 50 cents of that to reimburse the u.s. taxpayer, and keeps the other 50 cents, then both parties are now ahead, each by 50 cents. But the US government has given $1 of foreign tax credit when no foreign tax was in fact paid.

Blown up to size, this is STARS.

Simplified, the case is over whether STARS existed to get BNY a good interest rate by borrowing in the UK, or whether it was a "sham" designed purely to pump the US government for tax credits. Between 1999 and 2006, the IRS claims that the six banks which were involved in STARS took $3.4bn in foreign tax credits. Five of those banks are now included in lawsuits with the IRS, although Barclays itself hasn't been implicated in any wrongdoing.

Despite this, it looks like life will be difficult for the bank, which is one of the leaders in the high-stakes tax planning world. The IRS crackdown follows HMRC retroactively forbidding [3]Barclays from using a tax loophole in a "highly abusive" manner to buy back its own debt tax free. With governments worldwide facing pressure to pay down debt, and the "tax gap" being blamed for much of the difficulty, the bank is going to be facing an unprecedented level of scruitiny in its actions.