Hi, I want to Record the Advance payment to Vendor with PI Attachment, but system not support QB show - The entity Advance Payment does not currently support Attachable.

Welcome to Community, @useraccounts20.

You can create an expense account to record an advanced payment. Just make sure to have an acceptable file type of you PI attachment so you can attach it on your expense transaction.

To record an advanced payment:

1. Go to +New, then choose Expense.
2. Fill out the payee information. 
3. Under the Category column, select Account: Accounts Payable (A/P), then enter the description and the amount.
4. Click Save and close.

After that, scroll down towards the bottom of the page then click the Attachments icon. A window will open, find the location of your PI attachment then hit Open to attach it to your transaction.

Here's how it looks like.

To learn about the acceptable file types for attachments, check out this guide: Attachments in QBO.

Keep me posted if you still have questions or concerns with vendor transactions. I'll be around to help. Take care and have a good one.