XYZ Tech Solutions is a software development company that has entered into a contract with a client, ABC Enterprises, to provide a comprehensive business solution. The contract involves the delivery of software, training sessions, and ongoing technical support over a twelve-month period, making it a multiple-deliverables arrangement.

The delivered item has value on a stand-alone basis and can be sold separately.

In the case of XYZ Tech Solutions, each component of the business solution, including the software, training sessions, and technical support, is assessed for its stand-alone value. If a component has independent value and could be sold separately, it satisfies this condition.

The delivered item is not returnable.

To recognize revenue on separate units, it is essential that the delivered items are not subject to return. In the case of XYZ Tech Solutions, the software, once delivered, is non-returnable, meeting this condition.

Collection has occurred for all of the separate units.

For revenue recognition, XYZ Tech Solutions must ensure that it has collected payment or has reasonable assurance of payment for each of the separate units within the multiple-deliverables arrangement.

The separate units must be delivered within 90 days of the end of the accounting period.

There is no specific time constraint mentioned in the case, but it's crucial to deliver the separate units within a reasonable timeframe. XYZ Tech Solutions needs to manage its delivery schedule to meet this condition.

What is one of the key conditions that must exist for a company to recognize revenue on separate units under a multiple-deliverables arrangement?