Starting Thursday, most American families will start receiving a check for as much as $300 per child every month through the end of this year, as part of the $2 trillion American Rescue Plans expansion of the child tax credit that congressional Democrats passed in March.

The first set of payments, amounting to $15 billion this month to be sent out by the IRS, will reach more than 35 million American households, covering just under 88% of children in the United States, according to a White House official.

Heres what you need to know about the program.

History of the child tax credit and how it has changed

The U.S. has had a version of the child tax credit since the late 1990s. But its always been small. It began as a $400 credit in 1997 and has gradually increased since. And it was focused on reducing taxes. As such, it didnt put much extra cash into families pockets.

Children have long suffered the highest poverty rate of any age group in the country. For nearly two decades, Democrats have sought to not only increase the benefit, but to transform the tax credit into something that could also help the very poor.

Republicans, however, have been reluctant to change the tax credit into anything that resembled welfare or a direct-cash benefit. They doubled the child tax credit in their 2017 Tax Cuts And Jobs Act to $2,000 a year through 2025, but limited how much of the credit could go toward increasing a familys cash refund.

Then the coronavirus pandemic happened. Suddenly, Republicans and Democrats were signing on to direct cash payments the stimulus checks. When Democrats won full control of Congress and the White House, they also made changes they had long wanted to the child tax credit.

Democrats increased the credit to as much as $3,600 per child and made it fully refundable. All American families with incomes up to $400,000, including those that dont make enough money to pay taxes at all, can receive the benefit. And Democrats told the IRS to distribute the credit in advance, as monthly checks through December.

What families should expect

Families with a joint income of less than $150,000 will receive $3,600 per child under the age of 6, and up to $3,000 for children between ages 6 and 17, in 2021. Every child under the age of 17, born by the end of 2021 is eligible. Distributed monthly through December, eligible families will receive $300 per month for each child under age 6, and $250 for kids 6 to 17. The payments will be made on the 15th of each month, unless that date falls on a weekend or holiday.