By clicking on Quotes, the user can verify the details of Quote. A button to accept or decline the quote will appear in the detail view of a quote when it reaches the “confirmed” stage. 
If the user ‘Accepts’ the Quote, the status will be updated to “Closed Accepted”. 
After accepting the Quote, the ‘Proposal Status’ will also change to Converted. 
Similarly, you can also see the Status in your SugarCRM portal as Closed Accepted and Converted. But if the customer declines the ‘Quote’, they must add a Reason for Decline.  The status in ‘Quote’ will be updated as Closed Lost.
Similarly, you can also see the Status in your ‘SugarCRM portal’ as Closed Lost. 
Note: The customer can see the ‘Rejection History’ field because the admin has selected it during the Portal Layout setup.
Later, you can edit the “Quotation” on the basis of rejection reason and resend the same to the User. Admin can edit the quotation on the basis of rejection reason and resend the same to the user.
Note: This cannot be changed again from the portal.