The deputy governor of Tonga's Reserve Bank, Fineti Ah Hoy, says so far they've received 57 illegal notes handed in under a five-day amnesty period which ends on Friday.
The Reserve Bank granted the amnesty after illegal 20 pa'aga notes were recently found in circulation.
The Reserve Bank is keeping businesses informed about the illegal notes through media coverage and public meetings, and Mrs Ah Hoy says damage to business appears to be minimal.
"Businesses are not affected. These has been returned mostly from individuals and from the commercial bank. Now this is the first time we have experienced this type of problem, it has never happened before."
Deputy Governor of Tonga's Reserve Bank, Fineti Ah Hoy.