How to pay IRS by check?

[taxguyask]

My accountant filed extension on April 17 for me and paid estimated tax by my bank account along with the extension application.

I have not yet finished my tax calculation completely but notice I owe more than I paid.  Before I file the tax in the future, I want to pay NOW to reduce penalty and interest.  My accountant no longer works for me.

How do I pay more by check? What information I should give along with the check so IRS know I am paying more for last year's tax?

[Bees]

If you want to send in a paper check print out the 1040 voucher https://www.irs.gov/pub/irs-pdf/f1040v.pdf

If you want to do the same thing electronically use https://www.irs.gov/payments and make sure you indicate it is for the tax year 2017