Magento Shopping Cart Price Rule - Discounting the wrong amount

Question

We have a Magento store running 1.9 Community version.

We have a number of discount codes we publish in magazines, this morning we noticed however instead of giving a 10% discount it's giving a little bit more than it should...

Check this screenshot:

https://i.sstatic.net/LY1Si.png

10% of £97.87 = £9.79 - no problem

£97.87 minus the discount rate £9.79 does not equal £86.12

This is the settings for the code: https://i.sstatic.net/vSxf1.png What are we doing wrong here? I am at a total loss.

Answer 1

Here's what happens:

• You have 20% VAT.
• Your discount is set to be calculated on price including VAT: 9.79
• Your product price excluding VAT: 81.55
• Your discount is set to apply at subtotal, subtotal is excluding VAT: 81.55 - 8.79 = 71.77
• Grand total is subtotal after discount plus VAT: 71.77 * 1.20 = 86.12

So your fix is to calculate discount price excluding VAT or apply at subtotal including tax.

Answer 2

Maybe the discount it is subtracting adds some tax? There's a setting in config->sales->tax that says to calculate tax before or after discount and the setting below it specifies whether you calculate tax in the discount.