Hi and welcome to Just Answer!
I assume that you are asking about your 2012 tax return which is due before Apr 15, 2013?
If that is correct - you may file your tax return as soon as the IRS releases all required forms. Generally all basic forms are expected to be available by Jan, 1, 2013 - and you may file.
Another issue - if you prefer to file electronically - normally the IRS starts accepting tax returns around Jan 14 - you still might be able to file earlier - but your e-file provider will keep your tax return until the IRS opens the gate - and only after that - you will be able to have a confirmation that your tax return is received.

You may choose to mail your tax return - but in this case your tax return will be processed longer and if you expect a refund - it will be delayed.
Sometimes the Congress makes late changes in the tax law - that require corresponding changes in some tax forms - if that will happen this year - we may expect the delay with filing.

So - to address your question - yes - you may file your tax return by mail in the first week of January 2013 - but to expect faster refund - you better wait when the IRS starts accept e-file.

Let me know if you need any help.