Now it turns out the deal is even sweeter for the lenders than it appears: Taxpayers will subsidize them for the money they’re ponying up.

The Internal Revenue Service regards the lenders’ compensation to homeowners as a cost incurred in the course of doing business. Result: It’s fully tax-deductible.

Critics argue that big banks that were bailed out by taxpayers during the financial crisis are again being favored over the victims of their mortgage abuses.

“The government is abetting the behavior by not preventing the deduction,” said Sen. Charles Grassley, R-Iowa. “The taxpayers end up subsidizing the Wall Street banks after the headlines of a big-dollar settlement die down. That’s unfair to taxpayers.”

Under the deal, 12 mortgage lenders will pay more than $9 billion to compensate hundreds of thousands of people whose homes were seized improperly, a result of abuses such as “robo-signing.” That’s when banks automatically approved foreclosures without properly reviewing documents.

Regulators reached agreement this week with Goldman Sachs and Morgan Stanley. Last week, the regulators settled with 10 other lenders: Bank of America, JPMorgan Chase, Wells Fargo, Citigroup, MetLife Bank, PNC Financial Services, Sovereign, SunTrust, U.S. Bank and Aurora. The settlements will help eliminate huge potential liabilities for the banks.

Many consumer advocates argued that regulators settled for too low a price by letting banks avoid full responsibility for wrongful foreclosures that victimized families.

That price the banks will pay will be further eased by the tax-deductibility of their settlement costs. Companies can deduct those costs against federal taxes as long as they are compensating private individuals to remedy a wrong. By contrast, a fine or other financial penalty is not tax-deductible.

Taxpayers “should not be subsidizing or in any way paying for these corporations’ wrongdoing,” said Phineas Baxandall, a senior tax and budget analyst at the U.S. Public Interest Research Group, a consumer advocate.

Spokesmen for several of the banks in the mortgage settlement didn’t immediately respond to requests for comment. Bank of America and Citigroup declined to comment.

In some rare cases, federal regulators that have reached financial settlements with companies have barred them from writing off any costs against their taxes, even if they might be legally entitled to do so. The Securities and Exchange Commission did so, for example, in 2010 in a $550 million settlement with Goldman. That case involved civil fraud charges over the sale of risky mortgage bonds before the financial crisis erupted.

It was the largest amount ever paid by a Wall Street bank in an SEC case. But the SEC defined nearly all the $550 million as a civil penalty. That meant it couldn’t serve as a tax deduction for Goldman. The agency cited “the deterrent effect of the civil penalty.”

In that case, the SEC appeared to want to send a message at a time of public anger over Wall Street excess, said James Cox, a Duke University law professor and expert on the SEC. Cox noted that when they negotiate financial settlements, companies consider whether they can deduct some of their costs.

Similarly, when BP agreed in November to plead guilty and pay a record $4.5 billion in the 2010 Gulf oil spill disaster, the Justice Department got BP to agree not to deduct the cost of the settlement against its U.S. taxes.

The total BP will pay includes about $1.3 billion in fines. But it also includes payments of $2.4 billion to the National Fish and Wildlife Foundation and $350 million to the National Academy of Sciences. Normally, those payment would have been tax-deductible.

The banks that just settled with regulators over their mortgage abuses are getting off lightly, Cox suggested. When the amount companies must pay in a settlement ”is just the cost of doing business, there’s not very much deterrence value there,” he said.

At least one lawmaker, Sen. Sherrod Brown, D-Ohio, wants regulators to bar the tax deductibility of the lenders’ costs. Brown made his argument in a letter to Federal Reserve Chairman Ben Bernanke, U.S. Comptroller of the Currency Thomas Curry and other top regulators. The Fed and the comptroller’s office, a Treasury Department agency, negotiated the foreclosure abuse settlements with the banks.

“It is simply unfair for taxpayers to foot the bill for Wall Street’s wrongdoing,” Brown wrote in the letter dated Thursday. “Breaking the law should not be a business expense.”

Unfair, too, in the eyes of Charles Wanless, a homeowner in the Florida Panhandle who is fighting his lender over foreclosure proceedings. As Wanless sees it, the government is giving help to banks that it refuses to give to troubled homeowners, who still must pay their full share of taxes.

“The government comes after us for every little bit of money we have,” Wanless said.

Bryan Hubbard, a spokesman for the comptroller’s office, declined to comment on Brown’s letter. Fed spokesmen couldn’t immediately be reached for comment.