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Option 1: Do not add the question to Customer portal layout or Remove the question from Customer Portal layout that you want to completely hide from customer.
Option 2: Setup the Sensitivity Level for that question.
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Clone the active version to a new product version. Product Details
Go to Sales Process tab.Sales Process tab
Select Customer Portal in Layouts list.
Identify the question you want to hide on customer portal. For ex: you want to hide “Duration Of Travel” question.
Hover the mouse on the question and click button X to remove it.
Save the product version.
Publish the product version.
To verify the change, create a new quote on Customer Portal to see the change.
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