Fraudsters are using new websites containing 'Covid-19' in their branding to con businesses into ordering supplies that never arrive.
The Banking and Payments Federation of Ireland (BPFI) warned that two types of scams were particularly targeting small firms: fake invoices and invoice redirection.
Both seek to exploit firms' naiveté about making purchases and paying bills online, as they close shops and operate remotely for the first time.
The first scam involves fake e-commerce sites offering Covid-19 tests, anti-viral sanitisers and personal protection equipment for sale.
Interpol warns that hundreds of such websites - many with professional design and fake client testimonials - have been launched in the past month.
"Worryingly, over half of those domains which contain the word 'Covid-19' have been created for criminal purposes. They take orders for goods and issue invoices which unwitting and legitimate businesses are paying for - but the goods never arrive," said BPFI chief executive Brian Hayes.
The second scam uses the criminals' knowledge of the firm to masquerade online as their real-life suppliers and creditors. They seek changes to usual payment channels, citing Covid-19 disruptions.
"The request may look authentic, but on close examination, it is a scam. If the request is acted upon, the next legitimate payment will be made directly to the fraudster's account," Mr Hayes said.
The BPFI-led FraudSmart programme tells firms they should research new suppliers thoroughly; not click on promotional links in emails; never make payments based on email instructions; and call a known contact at the other firm before electronically transferring a single cent.
"Do not use the contact details on the letter or email requesting the change. Look up the number independently," FraudSmart advises.
Mr Hayes said firms should "immediately report any suspicious activity to their bank and their local Garda station".