According to court documents obtained by PEOPLE, Sheen is supposed to pay $55,000 per month toward the support of the former couple's 7-year-old twins Bob and Max. Mueller alleges that Sheen has paid roughly $21,000 in total for March and April, leaving a shortfall of a little over $89,000.
In March, Sheen filed court documents asking a court to reduce the amount of child support he pays. He argued he should pay less child support now, because he has seen a dramatic decrease in his income from when the child support agreement was made in 2011. According to the documents, Sheen was once making $613,000 per month while working on Two and a Half Man, which he left in 2011. The documents stated he now earns $87,384 on average per month.
Sheen, 50, and Mueller, 38, were wed in 2008 and filed separate divorce petitions in 2010.
In his interview announcing that he was HIV-positive, Sheen, 50, told Matt Lauer he was extorted for $10 million by people threatening to make his diagnosis public.
In February, Sheen said on The Dr. Oz Show that he would like to revisit the child support agreements he made with Mueller and former spouse Denise Richards, whom he also pays $55,000 a month to in child support for their daughters Sam, 11, and Lola, 10.
Sheen also faces a lawsuit from Richards, who in January sued the actor for $1.2 million, alleging he has not provided all of the financial support he promised toward the care of their children, Sam, 11, and Lola, 10.
Sheen's attorney did not immediately respond to a request for comment regarding Mueller's claim that he owes $89,000 in child support.
In January, he responded to Richards' lawsuit, saying in a statement to PEOPLE that it was about "nothing more than money, money, money."
"Denise Richards is not satisfied that she has received $660,000 tax free each year for almost 10 years," Sheen's attorney Martin Singer tells PEOPLE in a statement. "It is not enough money for her, besides the approximate $10 million she has received from Charlie under her short marriage."