The official payment date for the checks is Monday, according to the IRS, so "some Americans may see the direct deposit payments as pending or as provisional payments in their accounts" before that date.
Paper checks will being mailed out starting Wednesday.
There is nothing taxpayers need to do to receive the payments, which are worth $600 each for individuals who earned under $75,000 in 2019, and $1,200 for couples who earned under $150,000. Those with qualifying dependents will receive an additional $600 payment for each child under 17.
Payments are automatic for eligible taxpayers who filed a 2019 tax return; those who receive Social Security disability, retirement or survivor benefits; and those who registered for the first payment on the IRS's Non-Filers tool by Nov. 21.
The IRS will automatically make the payments to the bank accounts it has on file, and send paper checks or prepaid debit cards to addresses it has on file for taxpayers.
The IRS also says the payments will be "topped up as quickly as possible" if any additional legislation passes that increases the value.
President Donald Trump has been calling for the increased payments since the Coronavirus Response and Relief Supplemental Appropriations Act was passed by Congress last week. He reiterated his desire for the higher payments Wednesday morning.
Earlier this week, the Democrat-led House passed the Caring for Americans with Supplemental Help, or CASH, Act, which would increase the stimulus payments to $2,000 for eligible taxpayers. Virtually all Democrats and a few dozen Republicans voted in favor of the bill.
But the bill was quashed in the Senate, with Republican Majority Leader Mitch McConnell blocking it Tuesday. Later, McConnell introduced a different bill that ties the $2,000 payments to a repeal of Section 230 legal liability protections for internet platforms and the creation of a commission to study election issues, all of which were recently demanded by Trump.
As Congress debates, the $600 checks will be delivered. Here are some other useful links about the payments: