The tax office plans to start its clampdown on plumbers, gas fitters and heating engineers at the end of the month.

After the cut-off date plumbers face fines of 100% of what is owed and criminal prosecution.

HM Revenue and Customs set out a special tax plan for plumbers to put right their tax affairs in March this year and gave the industry until the end of August to come clean about outstanding tax owed.

HMRC then began using information held on people working in the plumbing industry to clamp down on those who have chosen not to come forward and take advantage of the Plumbers Tax Safe Plan.

Since June, HMRC has been using information gathered from many different sources to open investigations into hundreds of people who have failed to come forward.

In addition to penalties, defaulters can face criminal prosecution.

Under the PTSP, plumbers, gas fitters, heating engineers and members of associated trades who owed tax that they had not declared faced a penalty rate of up t0 20%.

They have until 31 August to arrange for payment.

Mike Wells, HMRC’s Director of Risk and Intelligence, said: “Plumbers who have notified us of their intention to disclose now have until the end of August to tell us what they owe and make arrangements to pay.

“We are determined to ensure everyone pays their fair share and, since 31 May, have begun a series of enquiries targeting people in the plumbing industry. More than 600 will be underway by the end of this month, with many more to follow. “

“We have left the PTSP disclosure route open and I urge anyone with unpaid tax to use it to come forward and avoid potentially lengthy and costly investigations. The penalty they will pay will still be lower than when HMRC catches up with them.”

Plumbers can disclose unpaid tax and make arrangements to pay by contacting the revenue online at www.hmrc.gov.uk/plumberstaxsafeplan
or calling 0845 600 4507.