Contracts allow you to refine the pricing of existing products in the system relative to what you want to take effect to the customer. This controls the rates of the products and package products provisioned to the customer if no provisioned rates are in effect.
In each contract, you will define the effective dates and then add contract rates that will indicate the products that will be affected by the contract along with their corresponding rates.
In case contracts or contract rates are removed/deleted from the account, the pricing engine will get the next available rate from the pricing hierarchy as outlined in the Pricing Overview.
Pricing Overview - An overview of how pricing is determined in BillingPlatform.