The banking head was found guilty of fraud in a ruling made a year ago when he was working at Banco Espanol de Credito as a chairman during the early nineties, El Mundo reported.
Mr Saenz received a sentence but both the prosecuting and defence teams appealed against the ruling.
According to the Spanish newspaper, the sentence, which was originally a six month jail term, has been upheld by Madridâs Supreme Court and extended to eight months.
It is not thought that the CEO will actually go to prison as Spanish law states that only first time offenders with sentences of over two years spend time behind bars.
El Mundo, without citing a source, claimed that the ruling by the appeals court will be confirmed during the next few days.
The Spanish bankâs CEO has been in post since 2002.
By Jim Ottewill