Normally I pay my self-assessment taxes at time of filing my tax return. So if any taxes on my income are due after the year closes, so My Tax I calculated Less Tax Deducted at Source Less Advance Taxes paid by me, if there is any tax due or left, I will have to pay interest on this tax, from the due date of tax return to the time I pay my such balance tax. This is apart from the interest on delay in paying taxes which I pay otherwise, so double interest counts if my balance taxes are unpaid at self assessment time, and I delay my tax return too.
I may say that I can deposit my balance taxes (self assessment taxes) timely and still not file a return. This will save me interest as I paid my due taxes, but why delay filing of tax return then.