The core principle of IFRS 15, as per the International Accounting Standards Board (IASB), is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services.

This core principle is achieved by applying the following five-step model:

1. Identify the contract(s) with a customer.
2. Identify the performance obligations in the contract.
3. Determine the transaction price.
4. Allocate the transaction price to the performance obligations in the contract.
5. Recognize revenue when (or as) the entity satisfies a performance obligation.

Each step in this model involves certain judgments and estimates, which are required to be disclosed under the standard.