I received four vouchers for $1656 each. They do not add up to the Tax owed ?

[xmasbaby0]

That is not what they are for.  Those 1040ES forms are for paying estimated 2019 taxes during each quarter of 2019. You can use them or choose not to pay estimated tax during the year.  If you expect to owe over $1000 at tax time, it is a way to avoid the underpayment penalty.

If you are going to mail in your 2018 tax due the form you want says 1040V

Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS and/or your state received the payment.