The last time I had to deal with timeshares, we looked at the other timeshares for sale in the same location at similar dates – the company actually kept a ‘catalogue’ of available timeshares that we were able to consult.
In the end, these were higher than what we were actually able to sell the timeshares for (as you would expect of asking prices), but they allowed us to complete the initial IHT return, and HMRC did not seem to have any problem with this approach.
Presumably, though, you are dealing with a timeshare that was not subsequently sold within a reasonable period. Since asking prices are public, but sale prices tend not to be, you may be stuck using the slightly higher values.
Taurean Drayak
Elliot, Bond & Banbury