Withholding on business trust distributions: payors must deduct tax on distributed income to resident and non-resident unit holders. Amendment requires payors of distributed income from business trusts of the specified character to deduct tax at the time of credit or payment: a defined withholding rate applies for resident unit holders, while deductions for non-resident unit holders and foreign companies must be at the rates in force; the amendment also refines the non-resident description and sets the effective date.