Business ownership
Companies House, accountant, and solicitor; notify HMRC for corporation tax and payroll
Some steps differ by region inside the country.
Where
Companies House for registered companies, and their accountant or fellow directors for the underlying agreements.
How
Search Companies House by their name to find every company where they were a director or a person with significant control.
Ask the accountant for the accounts, shareholder register, and any shareholders or partnership agreement.
Read the articles and any shareholders agreement, they usually set out what happens to shares on death.
Check whether there was a cross option agreement backed by life insurance, which converts the shareholding into cash for the family.
What to bring
A certified copy of the death certificate
The grant of probate
Company names or registration numbers
Sources
This is practical information, not legal, medical, or financial advice.