explain IFRS 15 Revenue From Contracts With Customers fourth principles?

Step 4: Allocate the transaction price to the performance obligations in the contract—an entity typically allocates the transaction price to each performance obligation on the basis of the relative stand-alone selling prices of each distinct good or service promised in the contract. If a stand-alone selling price is not observable, an entity estimates it. Sometimes, the transaction price includes a discount or a variable amount of consideration that relates entirely to a part of the contract. The requirements specify when an entity allocates the discount or variable consideration to one or more, but not all, performance obligations (or distinct goods or services) in the contract.

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