The TX4 is a purpose-built taxicab (hackney carriage) manufactured by The London Taxi Company, a subsidiary of Geely Automobile of China. From 2007 until their liquidation in 2013 it was manufactured by LTI. It is the latest in a long line of purpose-built taxis produced by The London Taxi Company and various predecessor entities. The design has evolved via several mutations from the Austin FX3 of the 1950s. TX4's immediate predecessor is the TXII.

The TX4 features a new front radiator grille, an updated interior design, updated front and rear bumpers, and a different rear vehicle registration number plate surround compared to the TXII. There are now internal headrests as a result of EU safety regulations. On the earlier models there were two headrests fitted to the central partition for the rear-facing tip-up seats, but on the later models these were removed as drivers complained and found them awkward for vision reasons.

The only engine offered in the UK is a 2.5 litre VM Motori R 425 DOHC diesel engine (rated at a peak 75 kW or 101 hp at 4,000 rpm and 240 N⋅m or 180 lbf⋅ft of torque at 1,800 rpm) mated to a Chrysler 545RFE five-speed automatic transmission. An Eaton FSO 2405 A five-speed manual transmission is also available.

In markets outside the UK the TX4 is also available with a 2.4 Mitsubishi 4G69 four-cylinder petrol engine, rated at 112 kW (150 hp) at 5,500 rpm and 212 N⋅m (156 lbf⋅ft) at 4,000 rpm. The only gearbox available with this engine is a Mitsubishi-built five-speed manual.

As was the case with its predecessors the TX4 is built on a fully boxed hydroformed ladder frame with a separate body.

The front suspension, as with its predecessors, is of the double wishbone type with coil springs and an anti-roll bar while the rear suspension uses a solid axle with coil springs and a Panhard rod.

Anecdotally the reason for there being no TX3 and the marque number going straight to 4 is because the engine was Euro 4 compliant, and also for the vehicle to have a connection with the famous Austin FX4. The diesel engine was then later updated to be Euro 5 compliant. Currently the latest version of the TX4 is now euro 6 compliant and fitted with 2.8 litre VM Motori engine. This will be the last version of the TX shape until the new shaped ZEC (zero emission capable) electric TX5 will take over estimated to be available at the tail end of 2017.