Although there are variations on the time certain vehicles require the periodic inspection, taxis and hire cars for example require more checks than private cars to ensure their safety compliance, for most of us we can follow the standard periods.
Mopeds – Which now includes certain electric scooters for example, as well as micro cars. These vehicles require their first inspection at 3-years-of-age, then every 2 years thereafter.
Motorcycles, quads and quadricycles – The first inspection is at 4 years, then every 2 years thereafter.
Private cars – Again, the first inspection is 4 years after registration, then every 2 years until the car is 10 years old, at which point the review is annual.
You will normally receive a notification that your first inspection is due.
Remember, if your vehicle goes beyond the required date, or your ITV has expired, you will not be permitted to drive it, not even to the test centre, and it must be carried on a grua, so it is worth making sure of the dates to avoid this.