People buying expensive items could find themselves under extra scrutiny from Monday as new money laundering rules come into force.
Some firms ignored fraud fearing repercussions for reporting it
People who want to pay more than £10,000 in cash for an item must go through extra checks to prove who they are.
Professionals like accountants who deal with company finances could face prison if they fail to report anomalies.
The extension to the Proceeds of Crime Act will now encompass more sectors, like casinos and estate agents.
The National Criminal Intelligence Service (NCIS) estimates that up to £25bn per year is laundered through the UK.
To try to crack down on the practice new rules are being brought in across Europe.
Firms including solicitors, accountants and estate agents will face greater scrutiny, with the staff having to note and report any suspicious activity to the NCIS.
Workers risk prosecution if they do not report suspicious transactions that indicate fraudulent activity.
They are not allowed to tell clients they have reported them.
Steven Philippsohn, a money laundering expert with legal firm Philippsohn Crawfords Berwald, said: "At present only 25% of frauds are reported in the UK because companies are worried about the damage reporting such crimes can do to their reputation, and criminals exploit this.
"As of Monday, UK firms can't sweep money laundering under the carpet," he added.
People who don't obey the new rules could be fined or sent to prison for up to five years.