Unbilled water users urged to call Thames Water hotline
Nearly 15,000 residents who use water but do not pay for it are being warned they face up to six years of back charges if they do not come forward.
Thames Water has targeted customers across the Thames Valley and London as part of a six-week amnesty to escape being charged, which ends on 3 March.
Of the 14,787 possibly unbilled customers identified, just 1,297 have got in touch.
Unbilled customers should call its free amnesty line to start payments.
The company supplies water to more than three million properties across London and the Thames Valley.
Mike Tempest, customer services director, said: "People confirmed as unbilled customers who do not take advantage of our amnesty could be in for a nasty shock - six years of water bills in one go.
"People who call our amnesty line have nothing to worry about. If we confirm them as unbilled, any back charges will be waived provided they agree to pay from now on, which is great news for them."
Thames Water said many older properties have been divided up over the years and in some cases no-one has informed the company of the change, meaning that separate bills have not been set up.
The same thing can happen if a developer builds a new property and connects it to the water network without fulfilling the legal obligation to tell the water supplier.