Fronting is a form of motor insurance fraud where a lower-risk person is falsely named as the main driver of a car, while the real main driver is listed as a named driver, to obtain a cheaper premium.
In one line: Fronting is fraudulently naming a low-risk driver as the main user to lower the premium.
How fronting works
Fronting commonly involves a parent declaring themselves the main driver of a vehicle that is actually used mostly by their child, so the insurer prices the policy on the parent's lower risk rather than the real user's.
If a young driver would be quoted 2,500 GBP as the main driver but the policy is taken out showing a parent as main driver at 900 GBP, the 1,600 GBP saving is obtained through a false declaration.
Because the policy misrepresents who really drives the car, an insurer can refuse a claim, cancel the cover and record the fraud, which makes future insurance harder to obtain.
Fronting vs a named driver
Having a genuine named driver is perfectly legal. The line is crossed when the declared main driver is not really the main user, because that misrepresents the risk the insurer is pricing.
The test is who actually uses the car most, not who owns it or who pays, so honest answers about regular use keep a policy valid.
Primary source: FCA: Insurance