UK small businesses need to be on heightened alert for fake invoices, following an alarming increase in this type of scam in the first six months of 2015.

Action Fraud has received reports from 749 businesses reporting falling victim to this sort of con between January and June 2015 alone. This compares with 603 victims in the whole of 2014 and 739 in 2013.

The true figure may be much higher as a result of under-reporting.

“It is important that employees are made aware of invoice scams and are ready to recognise the signs of fraud," said Pauline Smith, the head of Action Fraud.

Fake invoice scams typically involve fraudsters posing as a supplier before attempting to trick marks into changing the account details for invoices. A worker might innocently amend account details only for the organisation to later find out that they have been sending money to a fraudster rather than a genuine supplier.

The more details a fraudster has about an organisation, the easier it is to pull off this sort of trickery. Sometimes fraudsters are assisted by corrupt insiders feeding them information about genuine suppliers.

"Incidents of invoice fraud are under-reported and therefore it is difficult to know the true scale of this fraud type. However, what we do know is that this prevails across all types of business and no one type of industry is immune. Those organisations that are worried they may fallen victim to fraudsters should always report to Action Fraud,” Smith added.

The warning about the growing scam coincides with the height of summer, a time when fraudsters have been known to take advantage of experienced staff going on holiday, leaving less experienced or temporary replacements who may be less likely to spot an attempted scam.

Businesses of any size are at potential risk, but small businesses are likely to find it harder to recover if they are unlucky enough to get stung.

Surrey police recently revealed they are investigating two allegations where businesses appear to lost around £1m.

Top tips for business on how to avoid becoming victims of the scam can be found in an alert from Cifas here. ®