Для того чтобы привязать купон к конкретному пользователю передадите в массив $data ключ USER_ID
[CODE]$fields = array(
'DISCOUNT_ID' => 16,
'ACTIVE_FROM' => null,
'ACTIVE_TO' => null,
'TYPE' => \Bitrix\Sale\Internals\DiscountCouponTable::TYPE_ONE_ORDER,
'MAX_USE' => 1,
'COUPON' => $coupon,
'USER_ID' => 1,
);[/CODE]
[CODE]$fields = array(
'DISCOUNT_ID' => 16,
'ACTIVE_FROM' => null,
'ACTIVE_TO' => null,
'TYPE' => \Bitrix\Sale\Internals\DiscountCouponTable::TYPE_ONE_ORDER,
'MAX_USE' => 1,
'COUPON' => $coupon,
'USER_ID' => 1,
);[/CODE]