"The Estate is diligently working to resolve any remaining issues," attorneys for Aretha Franklin told PEOPLE

Aretha Franklin is being pursued by the IRS.

The Internal Revenue Service claims the singer, who died on Aug. 16 of advance pancreatic cancer of the neuroendocrine type at age 76, owes more than $6.3 million in back taxes from 2012-18 in addition to $1.5 million in penalties, according to court documents obtained by TMZ on Thursday.

“The IRS has filed its Proof of Claim in the ordinary course of the Estate proceeding,” attorneys for the Aretha Franklin Estate told PEOPLE in a statement.

“This is not a liquidated claim and it is disputed by the Estate. The vast majority of Ms. Franklin’s personal 1040 tax obligations were paid prior to her death – something she wished to occur. The Estate is diligently working to resolve any remaining issues,” the statement continued.

David Bennett, who is among those representing Franklin’s estate, told the Associated Press that at least $3 million in back taxes have been paid to the IRS. Additionally, Bennett said all of Franklin’s returns have been filed, adding that the IRS is questioning the filed returns and her estate is disputing what the IRS claims “was income.”

Bennett did not immediately respond to PEOPLE’s request for comment.

Elton John AIDS Foundation Commemorates Its 25th Year And Honors Founder Sir Elton John During New York Fall Gala - Show
Credit: Nicholas Hunt/WireImage

The claims come one month after Franklin’s last property in her hometown of Detroit was reportedly sold for $300,000.

In 2008, the property slipped into foreclosure due to $19,192 in unpaid taxes — an incident Franklin attributed to an attorney’s mistake. Public records show she paid the back taxes and recovered the house.

At the time of her death, the Queen of Soul left behind an estimated fortune of $80 million, according to celebritynetworth.com, but she did not have a will, the Associated Press confirmed.

“I tried to convince her that she should do not just a will but a trust while she was still alive,” Don Wilson, a lawyer in Los Angeles who worked with Franklin, told the AP. “She never told me, ‘No, I don’t want to do one.’ She understood the need. It just didn’t seem to be something she got around to.”

Franklin’s four sons Clarence Franklin, Edward Franklin, Kecalf Franklin and Ted White Jr. will split her estate equally. Franklin’s niece is acting as the executor.