How do pay IHT after probate granted as estate value has changed.

I am administering a deceased family member's estate, their assets were previously £324,000, so no IHT was paid. Grant of probate has already been given a while back. Since then, I have found a number of accounts, previously unknown, that push this figure over the IHT threashold of £325,000 I am now finally satisfied there are no more accounts, however HMRC is owed £11,000 in IHT. How do I go about paying this without using the telephone?

Hi
Please refer to the following Guidance - Pay your Inheritance Tax bill