Could not finish Payment with PayPal due to rounding issues

[alex-jungwirth]

When using the built in Payment Method "PayPal" (Express Checkout), I get some rounding errors:
I have the option: "store prices with VAT" in my store config.

Example with Tax: 19%

Product Price (gross): 21,95 €
Quantity: 4
Shpping Costs (gross): 7,95 €

Calculation for Cart:
21,95 * 4 + 7,95 = 95,75

Calculation in PayPal Checkout (ConvertPaymentAction.php):
Product Price (net) * quty + taxTotal + shipping (net)
18,45 * 4 + 15,29 + 6,98 = 95,77

Due to the diff the paypal payment will not work.

Error in Transaction:

L_ERRORCODE0 10413
L_SHORTMESSAGE0 Total mismatch. See additional message for details.
L_LONGMESSAGE0 The totals of the cart item amounts do not match order amounts.
L_SEVERITYCODE0 Warning

[dpfaffenbauer]

welcome to the world of tax calculation ;). We know this. Its due to how CoreShop calculates tax and how PayPal calculates it. CoreShop calculates it row based, so we calculate tax for every row, round it, and sum it. PayPal calculates tax for each tax-rate (so horizontal), it takes all net values and applies the tax-rate. Due to rounding, we get different results.

2 Solutions: Either increase the decimal factors (use eg. 4 numbers after the coma) to improve rounding issues. or create a OrderProcessor that calculates it back and removes the cent rounding. We already did that, I can provide the code for this next week.

[alex-jungwirth]

welcome to the world of tax calculation ;). We know this. Its due to how CoreShop calculates tax and how PayPal calculates it. CoreShop calculates it row based, so we calculate tax for every row, round it, and sum it. PayPal calculates tax for each tax-rate (so horizontal), it takes all net values and applies the tax-rate. Due to rounding, we get different results.

2 Solutions: Either increase the decimal factors (use eg. 4 numbers after the coma) to improve rounding issues. or create a OrderProcessor that calculates it back and removes the cent rounding. We already did that, I can provide the code for this next week.

yes please, u rock 👍