I think 'chassis check' means all the checks that are not directly related to the engine. Such as checking tyres, brake linings, suspension condition etc. These are all normally done anyway as part of the annual service schedule .
But if your car is set to display service reminders these take account of how the car is driven .If you regularly make short journeys on a cold engine, or thrash the nuts off it , or live in a very dusty environment etc its considered a hostile environment for engine oil . The system may remember the typical oil temperature, engine stress etc and call for more frequent oil and filter changes . It may be sufficient in some circumstances just to have an interim ,early, oil and filter change , not the full service with chassis checks. So its warning you these are also due.
But I agree with Kremmen. Annual servicing (or 12500 miles if it comes sooner) should be fine even if you only do a small annual mileage. But as the car becomes older avoid the temptation to skip annual services because the oil has only done a few miles. Engines that seldom get properly hot can build up water condensation , and possibly some dilution by petrol , in their oil .
