In Russia, income tax is 13% of your income. It will be charged not only until the salaries are received: they are subject to goods, pension contributions, most types of business.
The income declaration of 3 NDFLs is submitted for the past settlement period. There are strict rules to fill out this declaration, for example, errors, blots, incorrect information, blue handle or fuzzy letters are unacceptable.
According to the legislation, when paying for medicines or treatment, you can legally return a part of the funds spent on treatment - to get a tax deduction.
The relatively new method of reporting for all employers, which includes information about all persons who received payments from the tax agent, about acquired and paid income, is called 6 NDFLs.
Your children are not even 18, and your income are subject to a 13-interest rate? In this case, you are entitled to take advantage of tax deduction by personal income tax on children.
If you have a permanent source of income, from which taxes are expelled to the state budget, and you have paid for studies in the official educational institution, then you have the right to return funds (tax deduction) in the amount of up to 13%.