NEW YORK (CNNMoney.com) -- The IRS on Monday said it would begin sending out 130 million tax rebate payments aimed at boosting the economy on May 2.

The order in which tax filers will receive their rebates will be based on the last two digits of their Social Security numbers, when they file and whether they opt for direct deposit.

The IRS said it expects to send out more than 25% of all rebate payments within the first three weeks. Most people will get their payments by July 11.

Filing a 2007 tax return is a prerequisite to getting your stimulus rebate check. And to receive that rebate this year, you will need to file no later than Oct. 15. The rebate will be sent separately from any 2007 refund you may have coming to you.

The most clear-cut schedule is for those whose returns are filed and processed by April 15. Generally speaking, it takes the IRS about two weeks to process a return, said IRS spokesperson Nancy Mathis.

For those filing on April 15 or beyond, they should receive their rebate payments about two weeks after receiving their refund if they're owed one, the IRS said.

To be eligible for a full rebate, single tax filers must have 2007 adjusted gross income (AGI) below $75,000 and joint filers must have AGI below $150,000.

Single filers with AGI below $75,000 will get rebates of as much as $600. Couples with AGI below $150,000 will receive rebates of up to $1,200.

In addition, parents will also receive $300 rebates per child under 17; there is no cap on the number of qualifying children eligible.

The IRS has created an online calculator to help tax filers figure out whether they're eligible for a rebate and how large it would be.