With Billdu online store modules you can use our free modules to connect your online store with Billdu. Modules for OpenCart 2.x, OpenCart 1.5, Prestastop and WooCommerce cen be found here. There is a brief guide in each file how to set up the module in order for your invoices to be created or sent via Billdu.
Your API key and secret can be found it your Billdu account on the website under Settings - API.
A Shopify App can be found here. Log in to your Shopify account and either search for the Billdu app on the Shopify App Store or click on the link to download the app. Once accepted and successfully installed a new account with the same e-mail address as your Shopify store will be created at Billdu. Once an account has been created and linked with your Shopify store, Billdu will ask you when you wish to create and send your invoices.
Currently it's not possible to connect with Shopify to a Billdu account which has been created previously.
You have a free 14-day trial and you can use all features and test the behavior of your Shopify store at Billdu. After that period you will be billed by Shopify on a monthly basis. A monthly Premium subscription is necessary in order to run the Billdu app.
Please note that Shopify has quite a strict policy regarding the invoice payments from your clients therefore the section Payment Options (under Settings - My businesses) can't be accessed on the Billdu website.
If you have any issues or feature requests concerning the general usage of the API please use the issue section in this Github repository https://github.com/billduapp/api_documentation