Tamborine. In view of the later facts which are emerging,I am coming to the conclusion that "tax" as such is perhaps the wrong term being used here.
As I see it premiums to SW ceased some six years ago,but they were not informed of the death of the Life Assured.The policy would be put into "cold storage" where it has remained until now. It would have had a "surrender" value and this amount is perhaps what they are now paying out to you.
Despite the Late Claim aspect I would be inclined to approach SW in a gentle manner and suggest that perhaps they reconsider matters ie had you known of the existence of this policy six years ago then there would have been a valid claim for the full Sum Assured which they would have met.
I would also politely mention that they have had the interest on the full Sum Assured for the last six years.
In conclusion I would like to stress that the Scottish Widows have a great reputation in the Life Assurance business. I would say they are second to none.
Good luck and please keep me posted.