Each quarterly BAS is due on the 28th of the month following the end of the quarter.
However, if you lodge using the ATO Business Portal you are eligible for a 2 week extension, and if you lodge using a registered tax agent(like me!), you are eligible for a 4 week extension – this is for lodgement and payment.
For the December quarter only, the ATO acknowledge the Christmas and New Year period together with school holidays as meaning that many businesses are understaffed and as such, EVERYONE is eligible for an extension of time to lodge and pay their BAS until 28th February which is next week.
Note: this should not be confused with your monthly BAS or IAS which is still due today!