I filed as an individual this year and received my return check in the mail, but my amended refund is a fraction of the check I received.

[js195]

For 2019 I initially filed as an individual and received my refund within a week in the mail. Then I realized that I had to file as married because I got married at the end of 2019. I sent in an amended return with all of my wife's information and w2's. TurboTax predicted that our return would be significantly lower than the check I received for my individual return. I have not deposited or spent the check I received from filing as an individual to avoid using money that isn't mine to spend. Do i mail the check back to the IRS or do they mail a bill after the amend is processed? 

[VolvoGirl]

You can keep the first refund.  Then the amended return is only for the difference you get back or owe.  In fact you should not even amend until the first return has fully processed and you get the first refund or your tax due payment has cleared.  And make sure the original refund or tax paid shows up on the amended return.  You can confirm this by printing your amendment and looking at the 1040X. Line 18 should be your original refund amount and line 22 should be your additional refund.  If you paid on your original return it will be on line 16.  If there is an amount owed with the amendment, it will be on line 20.

You have to include a check for a tax due when you mail the amended return.  Do not use any vouchers that may print out.  If you have a refund they will mail you a check.  They don’t do Direct Deposit for refunds.