Former bricklayer Jeffrey Bakewell, 69, of Wickford set himself up as a tax adviser to crane drivers and other construction trades.
An investigation by HM Revenue and Customs revealed he kept around £300,000 from his clients’ false claims.
Bakewell’s clients made claims for travel and subsistence payments but HMRC investigators found these had been covered by their employers.
A total of £1,507,965 was paid to Bakewell between 2009 and 2015.
He kept £301,897 and used it to finance his gambling while the rest went to his clients.
Bakewell failed to register as a tax agent with HMRC as legally required, did not complete due diligence checks on his clients and failed to keep the records required by the Money Laundering Regulations.
Paul Barton, Assistant Director, Fraud Investigation Service, HMRC, said: “Bakewell had no financial qualifications and set himself up solely to advise people on fraud.
“He charged for advice on how to steal money from our vital public services but his appalling conduct has now put him behind bars.
“We will not allow criminals to attack the tax system and cheat the honest majority.”
Bakewell admitted tax fraud and was jailed for five years at Chelmsford Crown Court on Monday.
Confiscation proceedings to recover the money he stole have begun.
Money is being recovered from Bakewell’s clients for the false repayments by civil means.