IHT - Form IHT403 1986

I am trying to do IHT forms for an elderly relative. At the top of IHT403 ( https://assets.publishing.service.gov.uk/media/5f60b44cd3bf7f7234487bf0/IHT403-05-20.pdf ) it states "Fill in this form to tell us about any gifts the deceased made on or after 18 March 1986." 1986 - is that a TYPO ? No idea how I find records going back much more than 4 years let alone 40 years. Is it a case of ' if they did, you would know about it... else assume 'NONE' ? Can someone clarify ? Tnx.

Hi,

Please contact our Inheritance Tax team for advice.

Inheritance Tax: general enquiries

Thank you.