This seems to be the equivalent of Death Duty, as Richard Bevan advises his wife to distribute extra funds to his children while she is still alive, and not to accumulate wealth.
The Bevan Family Letters website is a micro-site of The Regency Town House website. The Town House is a grade 1 Listed terraced home of the mid-1820s being developed as a heritage centre and museum to focus on the architecture and social history of Brighton & Hove between the 1780s and 1840s. For further information about the Town House project see http://www.rth.org.uk.