How to pay advance tax on unexpected income?

if u sure u will get this income then u should pay advance tax

income generated unexpectedly is liable for interest(as decided in the case of Mrs prabha lal) as if that income is a regular income and not unexpected.
how ever if such income is of nature like capital gain then interest on that portion is charged from the date of it's occurring.
please consult your tax consultant before taking action.

calculate the tax liability net of tds (if any) nd then pay within due date of 4th instalment i.e. 15th of March

interest on income fron capital gains is not charged for prior payment dates. This can be easily verified by the Excel and java utility published by ITR dept. however payments become due with the next advance tax payment date.