A former finance assistant at Autism Together has been jailed for stealing £120,000 from the charity.
Dale Mills, 37, from Leasowe, Wirral, pleaded guilty to two counts of fraud at Liverpool Crown Court.
He was sentenced to 32 months in prison for the crimes, which were committed over four years.
In a statement, Autism Together said Mills, who joined the charity in 2001, was a trusted and highly regarded member of its finance team before his crimes came to light in December 2016, the month in which he resigned.
"He was generally the main point of contact with the finance department when families had questions about service users’ financial positions," the charity said.
"Mills abused this position to divert money to his own accounts and create false accounting records to cover this up."
Founded as the Wirral Society for Autistic Children in 1968, Autism Together had an income of £21.2m and employed 967 staff in the financial year ending 31 March 2018, according to its latest accounts.
Most of its income comes from statutory bodies.
The charity, which is based in Bromborough, Wirral, said external auditors "did not identify weaknesses" in its long-standing internal controls.
Asked if it had changed anything to prevent a repeat, the charity said: "There has been a change in the senior management of the finance department."
It added that it was "seeking to recover the stolen funds via a number of avenues".
Robin Bush, chief executive of Autism Together, said the charity was "deeply shocked" to discover the fraud and sorry for any inconvenience to beneficiaries and their families.
Bush added: "We have made sure that no one has been disadvantaged by Mills’s actions and our organisation’s finances remain robust.
"We owe a huge debt of gratitude to Merseyside Police for their extremely lengthy and detailed investigation and also to our finance team who have worked diligently to understand the extent of Mills’s actions.
"We have set up contacts within our organisation for any families needing additional reassurance and our training team has developed support materials to help staff explain what has happened to any service users who might be concerned."