In the 2012 BIR tax calendar, the due dates were indicated even if they fall on a legal holiday, Saturday or Sunday. For example, e-filing for Forms 1601C for e-filers under Group B for the month of December is lodged under January 14, Saturday.
We have not encountered any formal issuance or announcement that the old rule (i.e., the due date falling on a Saturday, Sunday or holiday shall be moved to the following working day) has been revoked.
Nevertheless, taxpayers, whether filing manually or electronically, are well-advised to follow the deadlines as provided in the BIR tax calendar to avoid the risk of being assessed corresponding penalties for late filing of tax returns. Taxpayers, filing manually are advised to file their tax returns not later than the Friday in case the last day for filing the tax return falls on a Saturday, Sunday or legal holiday.