Retailers are continuing to hand out old £10 notes despite them ceasing to be legal tender on 1 March 2018.
However, the Bank of England has not asked shops to stop giving them as change, which could cause issues as £2bn effectively becomes unspendable.
The British Retail Consortium said: “It did not expect to see retailers giving out old notes right up to the deadline.”
The Federation of Small Businesses (FSB) said it is urging high street banks to continue accepting old £10 notes after the March deadline, in order to save small firms and the public from having to call on the Bank of England every time they need to swap “paper for polymer”.
FSB National Chairman Mike Cherry said: “A new £10 note that’s harder to fake will be largely welcomed by the small business community. Too often, it’s small firms that bear the brunt of counterfeiting.
“Hopefully, we won’t see the kind of upheaval that came with the introduction of the new £1 coin towards the end of last year. The vending and entertainment machines hosted by small firms are usually more reliant on coins than notes.”
He added: “That being said, there are more than £2bn worth of paper £10 notes still in circulation. Clearly, they won’t all be spent by Thursday. Small firms are working hard to prepare for Thursday’s change but will need support as the switchover takes effect.
“The more shoppers and business owners feel they can rely on banks to accept paper notes after Thursday, the quicker we’ll have them out of circulation.”