How can I efile when a dependant passed away in december

[Critter-3]

If the efile will not go through then you will need to paper file the return. 

[Opus 17]

Just file your tax return normally.  In the dependent interview, there should be a check box for "this person died during the tax year."

If you have tried e-filing and are blocked, then you just can't e-file.  Print your return and mail it.  Sometimes the IRS blocks the social security numbers of people who have died to prevent tax fraud.