The money deposited in the bank is called the principal; The extra money paid by the bank when withdrawing money is called interest; The ratio of interest to principal is called interest rate. Interest = principal × annual interest rate × time. Tax payment is to hand over a part of the collective or individual income to the state according to the relevant provisions of the national tax law. Taxation is one of the main sources of national income. The state will use the tax collected for the development of economy, science and technology, education and national defense. People often deposit temporarily unused money in banks for savings. Savings can not only support national construction, but also make personal property safer and more planned, and also increase some income. The tax paid is called the tax payable, and the tax payable and various incomes (sales, turnover ...) are called the tax rate.