Issue in rounding adjustments

[mattbrailsford]

Which component is this issue related to?

Umbraco Commerce (Core)

Which Umbraco Commerce version are you using? (Please write the exact version, example: 10.1.0)

13.2.3

Bug summary

It is not correctly rounding numbers and so the totals on some orders are not correct

I went through the Commerce issue tracker with them to see if we could find something useful and we stumbled across this one. Customers says that their issue is similar however, this issue was solved in 13.1.13 so it can't be the same. Any inputs on what we can look into?

Specifics

Rounding is set to Line, although they tried it with Total as well and still got the same issue. Prices include tax is set to false. The order in the screenshot has a 15% discount applied to both products

Steps to reproduce

MB Successfully reproduced

Expected result / actual result

No response

Dependencies

No response

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This item has been added to our backlog AB#55539

[mattbrailsford]

Issue has been fixed and will be released in 13.2.4 and 16.3.0

[ben637]

Hi @mattbrailsford,

I'm not sure whether this needs to be raised as another ticket but there is another issue we are experiencing with the discounts rounding.

It seems that when we call the following:

var totalDiscount = currentOrder.GetTotalPriceAdjustmentByType();

The total of the discounts is calculated from non-rounded line item discounts. This then gives us a different total for the discounts than if you sum the line item discounts.

We have the rounding set to "Line" so I would have expected the totalDiscount variable above to equal the sum of the rounded line discounts. (unless I am misunderstanding the rounding setting)

This becomes apparent when we have (screenshot of frontend of the website):

The subtotal minus the discount does not equal the total (21.84 - 3.28 should not equal 18.58).
The values are retrieved using:

subtotal = currentOrder.SubtotalPrice.WithoutAdjustments.Formatted().WithTax //21.84
discount = currentOrder.GetTotalPriceAdjustmentByType(); //-3.28
total = currentOrder.TransactionAmount.Value.Formatted() //18.58

Here is the backoffice screen for the same basket

Extra info:
We are running 13.2.4
The first product is 0% VAT, the rest are 20% VAT
A discount of 15% is applied to all 5 products.

I think I can get around it by calculating the discount amount like this instead:
var totalDiscountCorrect = currentOrder.SubtotalPrice.WithoutAdjustments.WithTax - currentOrder.SubtotalPrice.Value.WithTax;

But would be good to confirm and fix as a bug unless I am mistaken?

Many thanks

Ben

[mattbrailsford]

Hmm, interesting issue 🤔

What price exactly does your 15% discount apply to? The unit price? Line total price? Or something else.

I don’t think we round the individual adjustments. The issue really is that we apply all the adjustments and then round the price. If we rounded the adjustments beforehand you’d end up with some other potential for rounding issues.

I’ll have to try and replicate this and see if rounding could be applied, but I get the feeling it can’t completely.

[ben637]

The reward was against Order Line -> Base Price. But I think I tried Total Price as well.
If it is expected, do you see any issues with me changing to using:

var totalDiscountCorrect = currentOrder.SubtotalPrice.WithoutAdjustments.WithTax - currentOrder.SubtotalPrice.Value.WithTax;
I suppose technically that covers all adjustments not just the Discount type.

Or is there a better recommended way of displaying the total discount applied to the order?

[mattbrailsford]

I think that’s a perfect workaround as the price is rounded at that point. And as long as you don’t have any fee based adjustments (ie positive adjustments rather than negative, discount, adjustments) it should equal the same as the discounts.

[ben637]

Ok thanks Matt.