The fiscal / taxable horsepower or just tax horsepower was an early system to calculate road taxation rates for automobiles in a number of key Western European countries such as the UK, Germany, Franc
Lagonda 14/60 This 2-litre car from 1925 was taxed based on a Fiscal horsepower rating of 14 (actually 12.9), whilst the engine output was approximately 60 bhp.
A Vauxhall 23-60 from 1922, with a 4-litre engine, attracting 23 hp in terms of tax, but producing 60 bhp at 2000rpm