Also known as: Tail light bulb, Rear Light Bulb, Bulb, tail light
OEM & aftermarket tail light bulb from top brands — compare prices, check fitment, order with free delivery
Browse tail light bulb from trusted brands. Compare prices, check vehicle compatibility, and order with fast UK delivery.
Tail Light Bulb buying guide — what to know before you buy
The tail light bulb — also known as the rear light bulb — provides the low-level red glow at the back of the vehicle that makes it visible to following traffic at night and in poor visibility. Unlike the stop/taillight bulb, the dedicated tail light bulb uses a single filament and does not double as a brake light. A failed tail light bulb is an MOT failure and carries a fixed-penalty if detected by police. Most modern vehicles use a T10 (W5W), W21W, or R10W single-filament bulb in the rear lamp cluster. Osram and Hella supply long-life OE-specification tail light bulbs for all major vehicle makes.
Common causes of tail light bulb failure
Tail lights are on whenever the headlights or sidelights are switched on, so their filaments accumulate far more running hours than stop or indicator bulbs. Vibration, voltage spikes, and moisture ingress into the lamp housing all accelerate filament failure.
High operating hours — tail lights often run for thousands of hours over a vehicle's life
Moisture in the lamp housing causes corrosion of the bulb contact pins
Vibration on rough roads can fracture the thin tungsten filament
Voltage spikes from alternator issues can blow multiple bulbs simultaneously
Identifying the right replacement bulb
Always confirm the base type before ordering. The most common pitfall is confusing the tail bulb socket with a nearby stop/taillight socket in the same cluster — they look identical but require different bulbs. The owner's handbook or the CarParts247 vehicle registration lookup will confirm the correct part.
W5W (T10 wedge): very common in side-marker and tail positions on European cars
R10W (BA15s): bayonet single-pin, used in many BMW and Mercedes tail positions
W21W: single-filament bayonet used where higher candela output is required
Check the cluster for a part number moulded into the plastic near each socket
Frequently Asked Questions
How do I tell if a tail light bulb has blown?
With the lights on, walk around the vehicle — a dark lens where the others are lit is a clear indicator. Alternatively, switch on the sidelights and check the bulb visually for a broken filament inside the glass.
Will a blown tail light cause an MOT failure?
Yes. All required rear lamps must be functioning and displaying the correct colour. A failed tail light is a category 1 defect and an immediate MOT failure.
Can I upgrade to LED tail light bulbs?
Yes. Use E-marked Canbus-compatible LED replacements to avoid dashboard warning lights. LEDs last far longer than halogen bulbs and provide sharper, more visible light output.
Is the tail light bulb the same as the reversing light bulb?
No. The reversing light is white and located separately from the red tail light cluster. They may use the same base type (e.g., W21W or R10W) but the circuits and lens positions are different.
