The amount of an employee's pay withheld by the employer and sent directly to the government as partial payment of income tax is called withholding tax.

From what I understand it is the tax on payments made to Non Residents and overseas entities

Withholding tax, also called retention tax, is a government requirement for the payer of an item of income to withhold or deduct tax from the payment, and pay that tax to the government. In most jurisdictions, withholding tax applies to employment income. Many jurisdictions also require withholding tax on payments of interest or dividends