Exhaust replacement cost.

For most cars, replacing the mid-section — the most common failure point — costs roughly £95–£340 fitted at a UK independent garage in 2026, and a full system (cat-back) around £210–£750. Small cars sit at the lower end and premium models at the top. Back boxes alone are usually the cheapest job. The catalytic converter is a separate, much pricier part (£400–£800+). Pick your model above for a model-specific figure.

Usually just the failed section — exhausts are made of separate sections (front pipe, centre, back box) joined by clamps or flanges. But corrosion rarely affects one section alone: if the tester or garage finds several sections thin or crusted, replacing the lot in one visit is often cheaper than doing them one MOT at a time, because the labour overlaps and old joints frequently shear during separation anyway.

Yes — an exhaust with a major leak is an MOT failure, and it can also push emissions readings over the limit, which is a separate failure. Surface corrosion on a structurally sound system is recorded as an advisory, but exhaust advisories turn into failures faster than most: once the corrosion is visible outside, the inside is usually worse. A sudden change in engine note is the classic first sign of a leak.

On a car you plan to keep, often yes. A stainless system typically costs £80–£150 more than mild steel but lasts three to four times longer — mild-steel back boxes on UK salted roads commonly last only a few years. On an older car you may not keep long, the cheaper mild-steel section usually wins. Either way, replace with at least OE-equivalent quality: the cheapest pattern parts corrode fastest.