Well, the name b2b e-commerce suggests that
It's an online transaction where buyer and seller interact and transact over the Internet
Both buyer and seller are businesses - as opposed to consumers or any other entity.
So, it will be totally different from b2c e-commerce
A b2b e-commerce system must have all the features or at least major features of a normal offline b2b transaction, such as
a. Sales are in bulk quantity
b. Prices are never fixed - It goes up or down with volume/quantity change
c. Higher the ordered quantity - Lower is the price per unit
d. There should be re-order facility as business buyers tend to buy regularly
e. There will always be bargain - so negotiation will be part of transaction
f. Credit is an integral part of b2b sales - So, it will always be part of terms/conditions
g. Buyer and seller jointly bear responsibility of after-sale service
h. Distribution is extremely important feature - buyers in most cases are resellers.
i. Since volumes are large - logistics plays important role
These are a few basic features of a b2b e-commerce platform. There will be more requirements for product-specific or organization-specific features such as govt ordering or OEM purchases. Overall, the online system must be more efficient and user-friendly to attract and retain customers as otherwise businesses will continue to follow offline process. And most important - please unlearn b2c e-commerce before embarking on designing b2b e-commerce - both are miles apart design-wise