To extend an authorisation for a Klarna transaction, login to the Klarna portal, go to Orders, select the order that you are looking for and click on Extend expiry date.
For Klarna transactions, the default authorisation time is 28 days. We generally advise merchants to capture within those 28 days because otherwise the transaction will expire.
There is a possibility that shipments are delayed (due to several reasons) which may have an impact on the time left for capturing the payment. In such cases there is a possibility to extend the authorisation of a transaction in the Klarna portal.
Access to the Klarna portal
Find more information here.