Grossing up

[Tim2223]

Hi everyone

Looking for a little advice if I may.
Probate Granted on estate then we were informed HMRC is doing compliance check.
The estate is..
house and attached cottage plus a bit of money.
4 beneficiaries
1 gets attached cottage free of tax and as is not quite a quarter of estate a small part of rest of estate.
1 gets a income only trust which reverts to 2 beneficiaries on passing of this person.
2 get the other half equally
Solicitor submitted the whole estate and as had his late wifes exemption plus main residence, tax was minimal as only just over threshold.
HMRC have picked up on the cottage being free of tax in will and have grossed up to a bill of another 13k
We think solicitor messed up.
Can the cottage be included twice in calculations? So for the initial calculation for tax at 40% (which it was) and then again in grossing up?
We find it awfully confusing
Any help would be very much appreciated.
Many thanks
Tim

[Tim2223]

Just wondering, to make it less complicated. Can something (part of estate) that is left free of tax (solicitor definitely messed up) be taxed twice ? I.e included in whole estate for total inheritance tax and then also grossed up.
How serious a mistake is it to miss "free of tax" in second paragraph of will if you are a solicitor on nearly £300 per hour. We have lost trust and wondering if our feelings are warranted.