“The first batch of payments will be sent by direct deposit, which some recipients will start receiving as early as this weekend, and with more receiving this coming week,” the Internal Revenue Service said in a statement Friday. “Additional batches of payments will be sent in the coming weeks by direct deposit and through the mail as a check or debit card. The vast majority of these payments will be by direct deposit.”

A Treasury official told reporters the department didn’t yet have an estimate for how many payments would be sent in the first round on Friday.

Some payments may appear as pending or as provisional payments in bank accounts before the official payment date of March 17, according to the IRS. Starting on Monday, recipients will be able to check the status of their money on the IRS’s “Get My Payment” online portal, a Treasury official told reporters.

Biden signed the $1.9 trillion stimulus legislation into law on Thursday, a package that includes more than $410 billion of direct payments for most Americans. The payments mark the third direct cash infusion in less than a year.

Read: How to track the status of your third round IRS stimulus check

The IRS has not yet released a date for when Social Security and other federal beneficiaries will receive their payments, which will be sent the same way as their regular benefits. A payment date for this group will be announced shortly, the agency said.

Payments in the form of checks or debit cards will take longer than electronic transfers. Those mailed payments will start arriving before the end of the month, an IRS official told reporters. The government also does not yet have a breakdown of how many people will receive an electronic transfer, versus the money in the mail.

For those whose tax returns have already been filed and processed, the IRS will use income data for 2020 to determine eligibility and size of payments. For people who have yet to file, the IRS will review 2019 tax data to determine the payments. The IRS will review 2020 returns as they come in to see if people are owed more, and automatically deliver supplemental payments without taxpayers needing to take further action, the agency official said.

IRS and Treasury officials said they’ve also taken steps to ensure payments don’t go to temporary bank accounts that have since been closed. Some individuals who used H&R Block and Intuit’s TurboTax to prepare their returns complained that previous stimulus payments went to accounts set up by the preparer that were no longer active.

The IRS and Treasury worked with financial institutions to address the issue, and developed a way to quickly re-route payments sent to incorrect or closed bank accounts back to the government—allowing them to be reissued.

The IRS and Treasury officials said they’ve also put some controls in place to ensure payments aren’t sent to people who shouldn’t receive them, such as deceased individuals. But the government doesn’t have up-to-the-minute information on households, so there will still be some margin of error, they said.

The law states that the payments cannot be offset to pay various past-due federal debts or back taxes, the IRS said.