Here are the steps to merge the vendors in Moon Invoice:

1. Open the Moon Invoice application on your device or tap on this link.
2. Go to Purchases ➜ Vendors.
3. Click on the edit icon and select the vendors you wish to merge.
4. Tap the Merge icon, and in the Merge Vendors pop-up, choose the vendor you want to keep as the primary vendor.
5. Click on Merge and enter your account password to complete the process.