"The 4% figure excludes those who are the first of a married couple to die,"
Not always. HMRC figures say that 222,800 estates that applied for probate, 27,800 paid IHT.
Of those 222,800 estates, the deceased person was
married 24%
widowed 54%
divorced/single 22%
Unfortunately, the figures don't say how many of each group actually paid IHT, just the average amounts that were paid.
The figures say that the average married person left an estate worth £473k, a widowed person £450k and a divorced/single person £396k.
A number of married people did pay IHT on their death. I presume that they left assets to people other than their spouse.
The average IHT paid by each group was:
married £7,200
widowed £28,900
divorced/single £44,700
Since the average IHT for those that were married is much lower than widowed but the average value of the estate is similar this would imply that a much smaller number are paying IHT.
This would seem right as likely most people would be passing everything, or most, onto a surviving spouse.
But most isn't everyone.
There certainly are married people who are paying IHT on their death. So, it is likely that the real figure is higher than 4% but how much higher is open to question.
I certainly wouldn't say it was double as, already, there are a large number of divorced/single people included and there are already married people included as well in that 4% figure.
Source: Inheritance Tax liabilities statistics Table 12.4
https://www.gov.uk/government/statistics/inheritance-tax-liabilities-statistics