A serious pitfall where a sole trader of a business dies is cashflow.
The business accounts will be frozen as well as the personal ones and suppliers and employees will need paying to keep the business going. The IHT account may take time to prepare, given the business assets involved and the death of the prime business person!
There is the possibility of a special emergency interim grant of probate (ad colligenda bona) before a full IHT account is prepared if it appears that the business may be damaged in the period before the grant. A clearance letter from HMRC is needed. It is relatively rare but very useful.