Probably the previous owner has removed the ABS bulb to hide an underlying issue. You'd need out it on VAG-COM / VCDS to identify what fault codes are bought up, you'll then need get a new abs bulb unit once fixed as it the ABS light must light up and go out to pass an MOT. Usually it's just a speed sensor that goes, cheap fix, but could be a bigger issue if previous owner has gone to the trouble of removing the bulb! You can either 1) confront them and ask 2) turn up with vag-com/VCDS to see what the fault is 3) walk away Pete