In most circumstances when someone dies the executors have to apply to court for a Grant of Probate (or Letters of Administration if there is no will).
To get probate the executors will have to find out the value the estate at the time of death, submit all of the necessary information to HMRC stating the value of the estate and pay any inheritance tax due from the estate.
Valuing the estate will include fixing the price of your home and other property, shares, antiques, cash and other investment information. From this the executors will calculate how much if any inheritance tax is payable and apply to Court for a Grant of Probate.
Probate can take anything from a few months or more to be granted. There are also costs involved such as government fees, professional fees and taxes to pay.