I wasn't clear. The enormous sum (at a rate of 41% once the net investment tax kicks in) was to the IRS.  The Virginia income tax on the estate is only 6%, but still is a large amount on 700K taxable income. I have not found a voucher or an address where to mail it. I do have a voucher for a Virginia extension, with which I can mail that precise amount of the check, so I was thinking of doing that. I do that with individual returns that will owe a chunk of money, so I file an extension only to be able to mail them a check.