@ChrissyZ
First, if you qualify for a third stimulus check, you can get up to $1,400 for each taxpayer in your household plus $1,400 for each dependent. To find out if you are eligible and how much you can expect, visit the TurboTax Third stimulus check calculator.
See if you come up with the same dollar figure the IRS did.
If not, look at the IRS’s letter to see if they provide a reason for the lesser amount, and what method they suggest for you to contest its determination – you always have the opportunity for a second look. There could very well be some mix-up in their records.
You can also contact the IRS using a phone number dedicated to Economic Impact Payment issues.
See Coronavirus Assistance Impacts at the top of the IRS's Let Us Help You page for the number. Be aware, though, that live phone assistance is very limited at this time.
