Shops are still giving out old £10 notes days before they cease to be legal tender on Thursday.
According to the Bank of England about 200 million remain in circulation.
However, it has not asked shops to stop giving them as change, potentially sparking chaos as £2 billion effectively becomes unspendable.
The British Retail Consortium said it would not expect to see retailers giving out old notes right up to the deadline.
But major stores, including Tesco and Sainsbury’s, have said they would only stop giving them out after Thursday.
When the round pound was phased out last year many shops agreed to accept them beyond the deadline.
But Tesco and Sainsbury’s said they would not extend the deadline for the £10.
However, small shops have been urged to accept them beyond Thursday.
The Federation of Small Businesses, the trade body representing them, said they would need extra support for the changeover and called on banks to accept notes from both businesses and consumers after the deadline to help get them out of circulation as soon as possible.
The Bank said it did not expect all notes to be returned as some will have been destroyed, gone overseas or been kept as souvenirs.
The new polymer £10 notes featuring Jane Austen were introduced last year to reduce the amount of counterfeit money in circulation. Their design and plastic material makes them harder to forge and they are more robust.
Mike Cherry, FSB chairman, 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.”
He added that £2billion worth of £10 notes could not possibly be spent by Thursday. “Small firms are working hard to prepare for Thursday’s change but will need support as the switchover takes effect.
“We urge high street banks to continue accepting old £10 notes after Thursday 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.”
Andrew Cregan, retail payments policy adviser at the British Retail Consortium, which represents large retailers, said: “Customers should spend their paper £10 notes before March 1, after which they cease to be legal tender and retailers are not required to accept them.
“Paper £10 notes are of course legal tender until March 1, but we wouldn’t expect to see retailers to be giving paper £10 notes in change right up to the deadline.”