The An Post currency card for foreign exchange has been suspended until further notice.
In a statement last night, the postal service said that the UK's financial regulator has told Wirecard Card Solutions to cease all regulated activities.
Wirecard Card Solutions Ltd is the issuer of the An Post Money Currency Card.
This means that the 50,000 currency cards in use cannot currently be used by customers in Ireland or abroad.
The card is a prepaid MasterCard that allowed customers to buy 16 different currencies.
An Post said it "regrets this inconvenience to our customers and we are working to ascertain what impact this situation will have on customers who hold an An Post Money Currency Card".
No other services are affected.
They added: "An Post is actively engaged with our business partners for this product to ensure a swift resumption of services.
"Existing customers with further queries can contact the An Post Money Currency Card helpline on 1800 535 564."
Impacted customers are advised to keep an eye on the An Post website.