Any Individual or group of Individual or artificial bodies who/which have EARNED INCOME during the previous years are required to pay Income tax on it. The IT Act recognizes the earners of income under seven categories. These are: 

1. Individuals
2. Hindu Undivided Family [HUF]
3. Association of Persons [AOP]
4. Body of individuals[BOI]
5. Firms, Companies
6. Local authority
7. Artificial juridical person

Referhere for detailed instructions. 

The word Income has a very broad and inclusive meaning. In case of a salaried person, all that is received from an employer in cash, kind or as a facility is considered as income. For a businessman, his net profits will constitute income. Income may also flow from INVESTMENTS in the form of Interest, Dividend, and Commission etc. Infect the Income Tax Act does not differentiate between legal and illegal income for purpose of taxation. Under the Act, all incomes earned by persons are classified into 5 different heads, such as:

1. Income from Salary
2. Income from House property
3. Income from Business or Profession
4. Income from capital gains
5. Income from other sources

Gift exceeding Rs 25,000 is taxable unless it is received from any person who is a relative or on occasion of marriage or under will or by inheritance or in contemplation of death of the payer.

No.The dividend declared by Indian companies is not taxable in the hands of the share holders because tax on distributed profits have already been borne by the company. 

Yes.

No.

No.

Your agricultural income is not taxable per se. However, if you have any other source of income like income from INVESTMENTS, property etc, while calculating tax on them, your agricultural income will be taken into account, so that you pay tax at a higher rate on that other income.

Yes.

Generally the tax on income crystallizes only on completion of the previous year. However for ease of collection and regularity of flow of funds to the Government for its various activities, the Income tax Act has laid down payment of taxes in advance during the year of earning itself. Taxes may also be collected on your behalf during the previous year itself through TDS and TCS. If at the time of filing of return you find that you have some balance tax to be paid after taking into account your advance tax, TDS & TCS, the short fall is to be deposited as Self Assessment Tax .

Yes. This may take the form of interest if the return is not filed before the end of the assessment year. If the return is not filed even after the end of the assessment year, penalty may also be levied.. 

Yes. It may be furnished at any time before the expiry of two years from the end of the financial year in which the income was earned. For example, in case of income earned during FY 2006-07, the belated return can be filed before 31st March 2009.

It is never too late to start honoring your constitutional obligations for payment of tax. The department may ask you to file return of income for earlier years if it finds that you had taxable income in those years.

The excess tax can be claimed as refund by filing your income tax return. It will be refunded by issue of cheque or by crediting to your bank account. The department has been making efforts to settle refund claims within four months from the month of filing return.

Yes, provided the original return has been filed before the due date and provided the department has not completed assessment. However it is expected that the mistake in the original return is of a genuine and bona fide nature.

Theoretically a return can be revised any number of times before the expiry of one year from the end of the assessment year or before assessment by the department is completed; whichever event takes place earlier.