A Wall Street Journal investigation published on Wednesday found that taxpayers inadvertently paid duplicate Medicaid payments for hundreds of thousands of patients across the United States, wasting at least $4.3 billion in recent years.

According to the report, some of the nation’s largest insurance companies—such as Centene, Elevance Health, and UnitedHealth Group—received hundreds of millions of dollars each in duplicate Medicaid payments.

These errors occurred when Medicaid beneficiaries moved and began receiving coverage in a new state without being properly disenrolled from their previous state’s program. Between 2019 and 2021, states, which are primarily responsible for managing Medicaid, issued duplicate payments for roughly 660,000 patients each year.

According to the WSJ, more than 270 insurers received duplicate Medicaid payments between 2019 and 2021. During that period, Centene received $620 million, Elevance Health got $346 million, and UnitedHealth Group received $298 million in duplicate payments.

This massive taxpayer waste was highlighted by Trump senior adviser Elon Musk, who has been advocating for reduced government spending and significant budget cuts to various federal agencies.

“These are examples of medical fraud that the @DOGE team will fix,” Musk wrote on X, sharing a link to the Wall Street Journal article.

A representative from the federal Medicare and Medicaid agency informed the WSJ that the federal government is collaborating with states to tackle wasteful spending.

“Paying for a beneficiary’s Medicaid coverage in one state when that individual is already enrolled in a different state is a prime example of taxpayer dollars being mismanaged,” the spokeswoman said.

Centene, the insurance company, stated that it must continue coverage for Medicaid beneficiaries until a state officially disenrolls them.

A message sent from a Centene supervisor to staff in February stated, “Please DO NOT close cases when you learn a member has moved out of state. If the member shows eligible and are out of state, they can still can [sic] utilize some of the benefits.”