If you have just built your kit car (or got someone else to do it) and it has not been registered for road use before, ie it’s not a re-body of an existing car such as a VW Beetle or Toyota MR2 then yes it will need to go through the IVA examination as it will be classed as an ‘Amateur-built vehicle’
To clarify this is what the VOSA guidelines say;
“Amateur-built vehicle is one constructed or assembled for your own personal use, where:
the construction or assembly or a substantial part of it must have been carried out by you or other persons acting on your behalf; and a substantial part of the construction or assembly was carried out by you or other persons not involved in a business in the course of which motor vehicles are normally constructed or assembled”
IVA covers amateur built vehicles falling under the following categories;
“cars or light passenger vehicles with:
four or more wheels and not more than 8 seats - either actual or declared in addition to the driver's seat;
or
three wheels and not more than 8 seats in addition to the driver's seat and a maximum gross weight of more than 1000kg;
or
three wheels and a maximum gross weight of not more than 1000kg and an un-laden weight of more than 410kg i.e. not a motorcycle and either having a design speed of more than 50kph - 31mph.
or
an engine capacity more than 50cc.
or
light goods vehicles with:
three or more wheels; and a maximum gross weight not more than 3500kg. In certain circumstances, goods vehicles up to 5500kg can also use IVA.”