"We must be ready, we must vote the tax bill by (January 11), it is the most important issue," Stournaras told reporters after meeting Prime Minister Antonis Samaras.

The latest tax bill, the first part of a broader overhaul expected in April, broadens the tax base in the hope of increasing state revenue by about 2.5 billion euros (3.3 billion) this year.

It introduces new annual income thresholds for salaried taxpayers and scraps tax breaks for the self-employed, a category of taxpayer blamed for a large part of the tax evasion that has plagued state finances for decades.

Last month, European Union leaders agreed to provide 49.1 billion euros ($63.9 billion) in aid in return for more austerity measures.

Athens has already received 34.3 billion euros of this package and is poised to obtain another 9.2 billion euros at the end of this month if key fiscal reforms are carried out, followed by two more slices of 2.8 billion euros in February and March.

"The (next) Eurogroup will decide whether or not to make the next disbursement," Stournaras said.

This meeting by European finance ministers is expected on January 21.

The International Monetary Fund, which is participating in Greece's rescue, is also expected to decide by January 20 whether to release its next share of the bailout, worth an additional 3.4 billion euros, Greek reports said on Friday.