Calfornia's Department of Toxic Substances Control is missing $194 million.
State auditor Elaine Howle says officials that oversee contaminated cleanups have either not properly billed or collected more than 1,600 payments since 1987.
A portion of that total -- more than $13 million -- may never be recovered, as the statute of limitations for cost recovery has expired on the work.
Howle blames the lapses on "inadequate procedures and incomplete documentation."
In some cases, the department isn't sure just who is responsible for outstanding claims.
Toxics officials acknowledged the billing problem publicly last year and say they are working toward reforms.