Форум

$dbBasketItems = CSaleBasket::GetList(
    array(
        "NAME" => "ASC",
        "ID" => "ASC"
    ),
    array(
        "ORDER_ID" => $inv_id
    ),
    false,
    false,
    array("DISCOUNT_PRICE", "BASE_PRICE", "QUANTITY")
);
while ($arItems = $dbBasketItems->Fetch()){
    $discount += $arItems["DISCOUNT_PRICE"] * $arItems["QUANTITY"];
    $withoutDiscount += $arItems["BASE_PRICE"] * $arItems["QUANTITY"];
    $arBasketItems[] = $arItems;
}

$arOrder = array(
   "SITE_ID" => SITE_ID,
   "USER_ID" => $GLOBALS["USER"]->GetID(),
   "ORDER_PRICE" => ОБЩАЯ_СУММА_ТОВАРОВ,
   "ORDER_WEIGHT" => ОБЩИЙ_ВЕС_ТОВАРОВ,
   "BASKET_ITEMS" => ТОВАРЫ_КОРЗИНЫ
);

$arOptions = [];
$arErrors = [];

CSaleDiscount::DoProcessOrder($arOrder, $arOptions, $arErrors);

Bitrix\Main\Loader::includeModule('sale');

$arOrder = array(

'SITE_ID' => 's1',
'USER_ID' => $GLOBALS["USER"]->GetID(),
'ORDER_PRICE' => "0", // сумма всей корзины
'ORDER_WEIGHT' => "0", // вес всей корзины
'BASKET_ITEMS' => [
   //$fields
   [
      //'ID' => '49', 
      //'FUSER_ID' => '104', 
      //'ORDER_ID' => '', 
      'PRODUCT_ID' => '320830', 
      'PRODUCT_PRICE_ID' => '147710', 
      'PRICE' => '384.7800', 
      //'CURRENCY' => 'RUB', 
      'BASE_PRICE' => '384.7800', 
      //'VAT_INCLUDED' => 'Y', 
      //'DATE_INSERT' => '2017-05-12 14:43:25', 
      //'DATE_UPDATE' => '2017-05-12 14:43:28', 
      //'WEIGHT' => '0.00', 
      'QUANTITY' => '1.0000', 
      'LID' => 's1', 
      //'DELAY' => 'N', 
      //'NAME' => 'Бумага COLOR COPY белая А4,250г/м 125л.д/полноцв.печ. класс"А++"Австрия, белизн 161%(CIE), ш/к 43775', 
      //'CAN_BUY' => 'Y', 
      'MODULE' => 'catalog', 
      //'CALLBACK_FUNC' => '', 
      //'NOTES' => 'Розничная', 
      //'ORDER_CALLBACK_FUNC' => '', 
      //'DETAIL_PAGE_URL' => '/catalog/detail.php?ID=320830', 
      //'DISCOUNT_PRICE' => '0.0000', 
      //'CANCEL_CALLBACK_FUNC' => '', 
      //'PAY_CALLBACK_FUNC' => '', 
      //'PRODUCT_PROVIDER_CLASS' => 'CCatalogProductProvider', 
      //'CATALOG_XML_ID' => '', 
      //'PRODUCT_XML_ID' => '9003974443775', 
      //'DISCOUNT_NAME' => '', 
      //'DISCOUNT_VALUE' => '0', 
      //'DISCOUNT_COUPON' => '', 
      //'VAT_RATE' => '0.0000', 
      //'SUBSCRIBE' => 'N', 
      //'DEDUCTED' => 'N', 
      //'RESERVED' => 'N', 
      //'BARCODE_MULTI' => 'N', 
      //'RESERVE_QUANTITY' => '', 
      //'CUSTOM_PRICE' => 'N', 
      //'DIMENSIONS' => 's:68:"a:3:{s:5:"WIDTH";s:1:"0";s:6:"HEIGHT";s:1:"0";s:6:"LENGTH";s:1:"0";}";', 
      //'TYPE' => '', 
      //'SET_PARENT_ID' => '', 
      //'MEASURE_CODE' => '796', 
      //'MEASURE_NAME' => 'шт', 
      //'RECOMMENDATION' => '', 
      //'SORT' => '100',
   ]
]
); 

$arOptions = array( 
'COUNT_DISCOUNT_4_ALL_QUANTITY' => "Y", 
); 

$arErrors = array(); 

CSaleDiscount::DoProcessOrder($arOrder, $arOptions, $arErrors);
Bitrix\Main\Diag\Debug::dump($arOrder);
Bitrix\Main\Diag\Debug::dump($arOptions);
Bitrix\Main\Diag\Debug::dump($arErrors);