Tax at source will be deducted at the highest level on income accruing to people without permanent account numbers, following a new notification Wednesday that takes effect April 1.

The tax will be deducted at 20 percent or the highest prescribed rate for the category of income, whichever is higher, said a circular issued by the Central Board of Direct Tax.

"The law will also apply to all non-residents in respect of payments and remittances liable to tax deduction at source," a finance ministry statement said.

According to the new guidelines, assessing officer will not issue certificate for deduction at lower rate or zero-deduction unless an application bears the permanent account number, the government said.