Rep. Charlie Rangel’s ethics investigation turned up one unexpected twist: a loophole in House rules that permits Members to park unregistered cars indefinitely in the House parking garage even though it violates tax law.

The oversight came to light in the investigation of the embattled New York Democrat, who is facing 13 counts of violating House rules — and would have been facing one more were it not for lax parking regulations.

The House Committee on Standards of Official Conduct declined to charge Rangel for storing a 1972 silver Mercedes-Benz sedan in the garage for several years without registering it or applying for a reserved spot through the House Sergeant-at-Arms.

That’s because the House Garage and Parking Security office never enforced earlier, more restrictive rules prohibiting such conduct. Furthermore, the House Administration Committee has since exempted Members from the rules altogether.

“The applicable written parking policies prohibited the storage of vehicles in unreserved parking spots,” reads the ethics report dated July 21. “The investigative subcommittee’s inquiry found, however, that the written policy regarding storage was not enforced against Members. Under the current parking policy, Members are not prohibited from storing vehicles in unreserved parking spots.”

Until 2009, House parking policy prohibited Members and staff from parking vehicles, including motorcycles and bikes, in unreserved spaces in House garages, lots or designated on-street parking for more than 45 consecutive days.

But in the first meeting of the House Administration Committee in the 111th Congress — on Jan. 27, 2009 — it changed the rules without debate to shorten that length of time to 14 days.

When the committee did so, it reworded the rule so it applied solely to staffers.

“The reasoning behind inserting the word ‘staff’ probably was because if you reduce the time to just 14 days, what happens to Members who just fly home for August recess?” said Salley Wood, spokeswoman for committee ranking member Dan Lungren (R-Calif.). “They’ll automatically be caught in this sort of catchall.”

Wood said she doesn’t know why the time was shortened in the first place.

The change may have flown under the radar because when committee Chairman Robert Brady presented the minority with a document highlighting all the changes in the rules, the addition of the word “staff” wasn’t highlighted.

The Pennsylvania Democrat’s office declined to comment on why the change was made and why it wasn’t highlighted.

Ethical problems arise because Members who reserve indoor spaces are required to declare “imputed taxable income” based on what it would normally cost to park a car in Washington, D.C.

Each Member must declare $115 per month, meaning a Member parking in an unreserved space would essentially be evading nearly $1,400 of taxable income yearly.

Though Rangel’s Mercedes was towed from the House lot in 2008, he defended himself, according to the ethics report, by saying: “No one told me that the car shouldn’t be there. I had no notice and whatnot.”

The committee found this to be true: “While Representative Rangel appears to have stored his Mercedes for more than 45 days in violation of the parking policies, the actual practice of the parking office was not to take action against parking violations by a Member,” the report says.

“Because of that practice, the parking office did not provide any type of notice to Representative Rangel, as it would have to a staff member.”

It is not clear whether any Members other than Rangel have been parking in unreserved spaces for extended periods of time, but Roll Call has reported that Rep. Bobby Rush (D-Ill.) and former Rep. Melissa Hart (R-Pa.) have left cars in reserved spaces for several years.

But even if they are, House rules no longer ban the practice.

The ethics subcommittee recommended that the House Administration Committee re-examine the rule, citing concern over “the lack of enforcement of the parking policies established by House Administration.”

“Mr. Lungren takes seriously the suggestion that the policy be revisited and thinks that there’s a common-sense solution to prevent storage while accommodating the Members who are often back in their district for extended periods of time,” Wood said.

Brady spokesman Kyle Anderson said, “We look forward to the opportunity to review their recommendations and look forward to implementing the necessary and appropriate rule changes.”