A broker is usually not your tax authority; tax payment before withdrawal is a major red flag.
Usually no. Taxes are normally reported by the user to the tax authority in their country or region. A broker should not block withdrawals by demanding tax first.
A platform may request KYC, source-of-funds or account information, but it should explain the reason and timeline through official channels.
Support asks payment to a personal account, crypto wallet or unrelated company and says withdrawal is impossible without tax.