Income from interest on saving bank deposit

Hi All.

I am new to this forum.

I am a salaried man. I was quite put to distress by the Middlemen for filing of my Income Tax returns and claiming back the TDS from the authorities for quite a few years so i chose to go by the e-filing way from AY10-11

I have recently leant that income from Interest on Saving Bank Account deposits was taxable all these years.

I did not add the amount to my taxable income under the head 'Income from Other Sources' while filing e-retuns.

Each year the earning from interest was less than Rs 10000.

Now my query is

1) Can tax now be paid for AY10-11 and AY11-12?

2) What is the penalty?

3)How to do it through e-filing way?