2Checkout is one of the most popular online payment gateways to accept online payment from your international customers. For starters, you will need to have a 2Checkout account. Once you have that set up you will need to configure the payment gateway in the Zoho Invoice settings page.Once you have that set up you will need to configure the payment gateway in the Zoho Invoice settings page.

• Login to Zoho Invoice account and head to the 'Settings' tab.
• Click on 'Payment' sub-section and select Online Payment Gateways.
• In the payment gateway list, click on 'Setup Now' for 2Checkout.
• In the following page, enter the 2CO Account# and the Secret word
  
• Click on 'Setup' and you are done.

How to configure your 2Checkout Account.

• Login to your 2Checkout account.
• Head to the 'ACCOUNT' tab and then click 'SITE MANAGEMENT'.
  
• Ensure you have selected 'Off' for Demo Setting.
• Choose the 'Direct Return (Your URL)' option under Direct Return.
  
• Enter 'https://invoice.zoho.com/n/2checkout' in the Apporoved URL field.
• Click on 'Save Changes' and you are done.