The second part of the review will address the overall design of the system and is to be released in the spring next year, the OTS said.
Rachael Griffin, tax and financial planning expert at Quilter, said there has been a lot of press surrounding IHT and therefore there was perhaps an expectation to see more receipts.
She said: "It is a fact that there are some people who are not paying IHT when they should be, it can be confusing as and when the tax is due.
"A lot of the time people do not keep records of gifts made to individuals or in the event of something other than death, and this can lead to uncertainty surrounding payment of IHT.
"In the instance of a death, invariably a solicitor will have been engaged who pulls together all the requirements of IHT but this is not always so in the case of gifts.
Ms Griffin added: "The government has made it clear they wish to make IHT more simple and transparent, but this is true of all taxes.
"Simplification does not always mean adding to the process and whilst there is pressure on the Exchequer not to lose money, simplifying might mean making less people subject to the tax."