Gain on the sale of Section 1202 stock, which is qualified small business stock, is not fully taxable. This is because there’s an exclusion of gain for stock held more than five years. Assuming you satisfy this holding period test, the excludable percentage depends on when you acquired the shares:
An amount taken from income as a prepayment of an individual’s tax liability for the year. In the case of wages, the employer withholds part of every wage payment. Backup withholding from dividend or interest income is required if you do not provide the payer with a correct taxpayer identification number. Withholding on pensions and IRAs is automatic unless you elect to waive withholding.