I only want to allow certain customers to have access to bulk discounts, how can I do this?

You can restrict what types of customers have access to bulk discounts using a setting in your account.

Select Settings > B2B from the left menu.

Find the setting labelled Who should have access to bulk discounts.

Here you select who SHOULD get access to bulk discounts.

Regular visitors - this is any visitor that isn't logged into an account
Registered customers - these are customers logged into a normal customer account
Trade customers - these are customers logged into a trade account

Once you've selected who should have access to bulk discounts, remember to save your changes.