It’s three weeks after Christmas, but banks are still unwrapping presents.

In addition to President Trump’s tax overhaul — a move that can add billions of dollars to the bottom line of the country’s major banks — rollbacks on regulations could add even billions more in profits, thanks to fewer fines and less money spent on meeting regulations.

The improved prospects for the banks will come to light this week as Wall Street’s financial giants report 2017 results — and give outlooks for 2018.

Many fattened bottom lines will come on top of already-record profits.

Not that brighter futures for the banks were a secret to investors. The Trump administration has made no secret of its aim to cut regulatory red tape, tax and civil enforcement.

Shares of JPMorgan Chase, Citigroup, Bank of America and Morgan Stanley popped close to or more than 30 percent over the past year — easily outdistancing the S&P 500.

The gifts bestowed upon the banks by “Santa” Trump include:

Easing up on enforcement by installing bank-friendly regulators, like Mick Mulvaney, the new interim head of the Consumer Financial Protection Bureau;

Repealing rules that make it easier to bring class-action suits — hence pushing customers into arbitration, a bank-friendlier environment;

Granting additional waivers to banks over fines;

Cutting the income tax to 21 percent.

“Enforcement is always the key,” Anat Admati, a professor at the Stanford Graduate School of Business — and author of “The Bankers’ New Clothes: What’s Wrong With Banking And What to Do About It” — told The Post. “Rules mean nothing if you don’t enforce them.”

Banks may even get a break from the Federal Reserve.

“Changing the tenor of supervision will probably actually be the biggest part of what it is that I do,” Randal Quarles, the Fed’s top regulator, told bankers during his first public remarks on the job.

Late last month, the Trump administration granted three-year and five-year waivers to five banks — including Deutsche Bank, to which Trump owes about $130 million, even after it was found to have manipulated interest rates.

While the Obama administration had also granted one-year waivers to do business, the waivers offered by Trump’s regulators are three times and five times as long.

The Securities and Exchange Commission last year brought 17 percent fewer enforcement actions than in 2016 — the lowest level since 2013, according to a study by Georgetown University.

The amount of SEC fines also fell 15.5 percent, the study showed.

Some observers on Wall Street see it differently, however.

Bankers have long grumbled that the Obama administration used Wall Street as a piggy bank, levying fines for small infractions and scapegoating the industry over the financial crisis.

The Trump administration’s move to shield banks from getting punished by wronged customers — by shelving the rules in 2017 that gave a smoother path to class-action lawsuits — was called a “hard-fought victory for the banking industry” by its lobbying group, the American Bankers Association.

Already, investors are beginning to understand just how much the tax overhaul will mean to banks.

JPMorgan, led by Chief Executive Jamie Dimon, earned $4.23 billion last year. Dimon said on Friday the tax law change would add $3.6 billion to its bottom line in 2018.

Less known is what effect the tax overhaul and the added profits it will bring banks — plus the rate increases by the Fed — will have on bank customers.

No bank yet has said when — or if — it plans to raise interest rates paid to savings account holders.