Upgrade to V3

You can run Klarna V3 side by side with Klarna V2 and KPM (legacy). Also, do not uninstall your previous Klarna V2 ( or KPM - legacy), because there can be old orders that will need refund, capture and cancel for some time.

From Klarna V2

All you need to do is to Install Klarna addon. You can run Klarna V3 side by side with Klarna V2.

Do not uninstall the Klarna V2 version after going live with Klarna V3, only remove it from the checkout page. The V2 should be available in the backoffice to support cancel, capture and refund of old orders for some time.

From Legacy Klarna KPM (Kreditor)

Klarna V3 is a iframe based, therefore may need programmetic changes in your checkout page to render it. All information is available in install sections, and you may need to take a look at how it is done in Litium Accelerator.

Alternative:

It is easy to switch from KPM to Klarna HPP (Hosted Payment Pages). Simply, install Klarna addon, and use the Klarna HPP.

Do not uninstall the Klarna KPM after going live with Klarna V3, only remove it from the checkout page. The Klarna KPM should be available in the backoffice to support cancel, capture, and refund of old orders for some time.

ERP integration

If your ERP system does not support Klarna V3, consider an integration towards Litium from ERP using Litium Connect (Requires Litium 7.4 or later).

Your ERP system does not need to connect to Klarna V3 then, instead will talk to Litium, which will intern talk to Klarna.