Okay, first of all, SEAT dealers should have sold all their stocks of 1.2TSI 8V engined Ibizas before 2016, so, you need to work out if your engine does have a timing chain or a toothed belt to drive the timing gear.
VW Group introduced a replacement for the 1.2TSI 8V chain driven engines in late 2014, so I'd expect all 1.2TSI engined cars sold new by 2016 to have the later 1.2TSI 16V engine. To check which version of that 1.2TSI engine is fitted to your car, look under the bonnet and try to work out which side of the engine the turbo charger is mounted on - if the turbo charger is mounted at the front of the engine then your car does have chain driven timing gear, if the turbo charger is at the rear of the engine, the engine is the later version and has a timing belt.
Timing chains are not a service part, so that means that they are fitted for life or until they start to make noises that suggest that they are failing.
Unfortunately the same goes for timing belts, they should get checked carefully initially after maybe 8 years and replaced when starting to show signs of failing!
For me and probably some others, we will be planning to replace the timing belt and even some pulleys and tensioner after roughly 8 years regardless of if it needs replacing or not, really just to play safe and so attempt to avoid a large engine rebuild bill when/if that timing belt fails.
