Grant Thornton's 10th annual European Business survey, published last month, revealed that 87% of small and medium-sized firms in the UK did not think the introduction of the currency would affect their business.
"Whether the UK joins the euro currency or not, it is going to become a reality that will affect businesses," said Paul Andrews, author of the firm's SME Handbook. "From our survey it is clear that that the Government has not done enough to inform UK businesses."
The warning comes as large UK retailers which opted to accept the euro revealed some teething problems with their IT systems.
Marks & Spencer said its euro project was largely successful, but Elizabeth Nelson-Walker, head of the corporate IT project for the euro, said, "Some customers were not dealt with as planned due to an isolated fault with the system. A fix was sent out to all stores within a couple of hours."
Meanwhile, online retailers have been warned that they will need to price products in euros. "Firms that do not accept the euro must act now to tap in to the market," said David Sear, chief operating officer at e-commerce software provider WorldPay.