If you sell to other businesses (B2B), they'll usually need an invoice that shows the price of each item before tax, so they can reclaim the tax they've paid. In the UK, for example, this is a requirement for a valid VAT invoice.
If your prices include VAT, any customer whose Type is set to Business will automatically see each item's net price (excluding VAT) on their full-size documents. If you use Sales Tax, as in the US, your prices already exclude tax, so your documents don't change.
Setting a customer as a Business
On the customer's record in the Back Office, set the Type on the right of the customer record to Business. Customers are set as Customer by default, so you'll need to change this for any business you sell to.

Only set a customer as a Business if they're buying as a business. Private customers set as a Business will get documents showing prices excluding tax.
What changes on the documents
On documents for a Business customer:
- the Price and Line Total columns become Net Price and Net Total, and show the amounts excluding tax;
- discounts aren't shown, so each line just shows the amount charged. The Discount % column and the Merchandise Total and Discount Applied rows are hidden;
- the totals at the bottom are unchanged, so the business can still see the tax and the full amount to pay.

Which documents show net prices
For a Business customer, this applies to:
- the full-size receipt for a sale;
- the VAT invoice for a sale, from the customer's Purchase History;
- the receipt and invoice for a customer order.
It also applies to printed, emailed and texted copies. The 40-Col receipt doesn't change.
If an order is invoiced to a separate business, that business's invoice also shows net prices. See How do I split an invoice for a Bike Lease Order? for more details.