Good morning,

i need a module to change all product prices for a specific category.

Example: I want to increase / decrease the product prices for all articles of the category "towel" by 2% or 3,5€.

I didnt find a module that helps me doing it (Magento v. 1.9.4).

I was also looking for catalog price rules. Maybe someone can tell me how to modifiy the discount field, so i can enter negative discount values to add a price. In that case the discount should not shown in the shop, because it doesnt make sense to show a discount that value is higher than the original...

I hope someone can help me.

kind regards Chris

1 Answer 1


Magento doesn't accept negative discounts, i.e. price increases using catalog price rules. If you want to change this logic in your magento installation, you have to customize the Mage_CatalogRule_Model_Rule model and overwrite the _beforeSave() method (it is inherited from Mage_Rule_Model_Abstract):

Just remove the following code within that method:

 // Check if discount amount not negative
    if ($this->hasDiscountAmount()) {
        if ((int)$this->getDiscountAmount() < 0) {
            Mage::throwException(Mage::helper('rule')->__('Invalid discount amount.'));

Regarding what is displayed in your templates you might have to make some changes dependig on your theme / customizations etc. In Magentos default price template I guess you are safe regarding the display of a discount when your finalPrice is higher than the regular price.

I hope that helps.

  • Thank you for your answer, i removes this code and some other and i can add a negative discount now. But the price doesnt get a update.... Its still the same. Why? Feb 14, 2019 at 15:08
  • Hard to say, there are many possible reasons, please check your data in database tables according to this recommendations divisionlab.com/solvingmagento/…
    – HelgeB
    Feb 14, 2019 at 15:21
  • Thank you for your answer. I checked the products in the database assigned to that rule. This are 500 products, but i only have 60 in that category ... how i check which products are affected and how i can handle that? i dont know if the rule works atm Feb 14, 2019 at 19:04
  • I searched all product prices for that rule but got no entry! I rly dont know what to do now to affect my negative price rule.... Feb 14, 2019 at 19:13
  • please check the entries of the table catalogrule_product_price. There should be all your products with the correct prices. There are more entries for one product because you have the rules per day (and per other condition like customer group) and you have usualy data for 3 days in that table. If you find your correct input in this table you will have to overwrite Mage_CatalogRule_Model_Observer because you have some checks in the finalPrice calculation. I will put this in your second question.
    – HelgeB
    Feb 15, 2019 at 14:30

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