Since Postfinance is the preferred method of payment for more than 30% of online shoppers in Switzerland, integrating your Shopify store with Postfinance payments is a must-have for all shops operating in Switzerland. Luckily, there are options –

1. Wallee integration with Shopify
   Wallee AG is a Swiss based company who offer solutions for e-commerce payments and their system supports Shopify. Here’s how you can integrate wallee with your Shopify installation. It also offers all available payment methods, including PostFinance Card, PostFinance E-Finance, PostFinance E-Payment, TWINT, invoice, Paypal etc. 
   
2. PostFinance Checkout (via Wallee)
   You can also opt for direct integration with PostFinance using their software. The actual software used by PostFinance is branded wallee so it’s most likely using the same core. Transaction costs using this solution will be slightly higher.

You can decide which provider you choose. If you already have a payment processing contract with PostFinance you might opt for their solution for Shopify. If you need help and support, wallee is probably the better option as they are also a service provider and developed the original software, so you’re likely to get better customer support.