I would strongly encourage you to make your payment online with the IRS. In 2020, the IRS was months behind in depositing checks, some taxpayers got letters saying they owed the tax amount and penalties for not paying before the deadline. With electronic payment you will see the money come out of your account. Even if you mail in your return (I suggest only mailing if you have no other choice.). You can set up an account with the IRS and pay thru' that platform, but you can also pay without an account.
