1. Profits and gains from business and profession is the largest head of income under the Income Tax Act, covering everyone from small shop owners to large businesses.
2. There are two main parties involved - the assessee or tax paying entity, and the income tax department which collects taxes.
3. For an activity to be considered a business, it must involve trade, commerce or manufacture; have a profit motive; and be under the assessee's control.
4. Income from business is taxed based on net income (gross income minus legitimate expenses), not total sales. Certain income sources like rent from self-occupied property are taxed separately.