Police in Thessaloniki on Thursday detained the 48-year-old owner of an accounting firm who is believed to owe 10.6 million euros to the state.
She was to face a prosecutor later in the day.
Late on Wednesday, officers in the northern port city detained the 51-year-old former chairman of local soccer club PAOK for alleged debts of more than 1 million euros to the state.
The debts relate to a company which the 51-year-old is said to have worked for as a legal adviser. Dozens of suspected tax evaders have been arrested over the last couple of months as part of a drive to recover unpaid taxes.