If
you have already filed your tax return, you will mail your 1040-V/payment
voucher and your check or money order. You do not need to include your tax
return. https://www.irs.gov/pub/irs-pdf/f1040v.pdf
If you are paying additional taxes owed with your amended tax return or Form 1040X, you will include a check or money order with your amended return when you file it.
Amended return have to be printed and mailed in order to be
filed, per the IRS regulations. Three weeks after you have mailed your
amended return you can track it by visiting the following link: Where is my Amended
Return or by
calling the toll-free telephone number 866-464-2050.