You will need the following details of the person who died. Date of birth, national Insurance number, driving licence number, vehicle registration number and passport number.
You’ll also need the details of any benefits or entitlements they were getting, for example State Pension, details of any local council services they were getting, for example Blue Badge, the name and address of their next of kin, the name and address of any surviving spouse or civil partner, the name, address and contact details of the person or company dealing with their estate (property, belongings and money), known as their ‘executor’ or ‘administrator’ and
details of any public sector or armed forces pension schemes they were getting or paying in to

This explains it all: www.gov.uk/tell-dvla-about-bereavement/