# Klarna checkout V3 US sales tax
**URL:** https://forum.litium.com/t/klarna-checkout-v3-us-sales-tax/1512
**Category:** Questions
**Tags:** litium-7
**Created:** [June 2, 2020, 9:38am UTC](https://forum.litium.com/t/klarna-checkout-v3-us-sales-tax/1512 "2020-06-02T09:38:52Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@christian.vejrich](https://forum.litium.com/u/christian.vejrich)
#### Post date: [June 2, 2020, 9:38am UTC](https://forum.litium.com/t/klarna-checkout-v3-us-sales-tax/1512/1 "2020-06-02T09:38:52Z")
Hello!
We want to implement US sales tax in Klarna checkout V3 using the Litium plugin for Klarna.
Klarna has the possibility to do a post request when the address in Klarna is changed by the customer. We already have an endpoint ready on our side(Merchant side) to calculate US Sales tax based on customer address, but how do we configure the callback URL in the Klarna V3 config file?
Thanks!
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### Author:  [@NilsN](https://forum.litium.com/u/NilsN)
#### Post date: [June 4, 2020, 7:20am UTC](https://forum.litium.com/t/klarna-checkout-v3-us-sales-tax/1512/2 "2020-06-04T07:20:03Z")
When the payment args for Klarna are created, we send this line:
`checkoutFlowInfo.SetValue(ConstantsAndKeys.AddressUpdateUrlKey, updateAddressUrl.AbsoluteUri);`
The URL sent goes to the `AddressUpdate` action in `KlarnaPaymentController`, which I believe is what you’re looking for.
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### Author:  [@system](https://forum.litium.com/u/system)
#### Post date: [July 2, 2020, 7:20am UTC](https://forum.litium.com/t/klarna-checkout-v3-us-sales-tax/1512/3 "2020-07-02T07:20:09Z")
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