More than $600m (Sh60 billion) worth of Kenya's old 1,000 shilling notes have yet to be turned in with just hours before the deadline for demonetisation of old generation notes.
Central Bank of Kenya (CBK) remains at a loss as to where the cash could be, but is making a final push to find it.
CBK Governor Patrick Njoroge on Monday said well over 70 per cent has already been returned.
The demonetisation aims to curb illicit financial flows in the country.
According to the Africa Tax Justice Network, Kenya has been losing $400 million (Sh40 billion) every year since 2011 through illicit financial flows.
On May 31, the Kenyan government issued a Gazette notice saying the old generation notes cease to be legal tender on October 1st.
In August, Patrick Njoroge admitted there was fake new currency in circulation.
