Interest calculation for old tax due

The assessee is liable to pay not only interest u/s 234 b but also under 234 c and 220. All the interest are to be paid and if assessee doesnot pay tax then return will be taken as invalid and 234 a will also come into play. Kindly handle with due care. There are endless possiblities of consequenses. Demand notice hasnt been furnished? If so interest on that also has to be taken. Best thing yoi can do is approach cit for payment of tax and interest and ask him to condone any penalty if so which would arise by bringing up this old case again.