Prelim Tax calculated incorrectly

Hi

I submitted my 2011 preliminary tax in October last but now have discovered that it is short by about 2k. Do I contact revenue now and make a second submission or do I leave it until I am paying the full tax next October. Do they charge penalties or interest and if so how much. It was an estimate to the end of the year but circumstances suddenly changed.

Thanks
jemol

You will be subject to interest charges if the preliminary tax you paid was less than the lesser of:
90% of your final 2010 liability or
100% of your final 2009 liability.

If you are short of this, just make an additional payment now (through ROS or by cheque to the Collector General).

Is it 100% of the 2009 liability? If so, your OK.

I would pay it immediately using the online facilities. This will lessen the burden of any interest that they do apply.