Deferred revenue, also called unearned revenue, is money a company has already collected from a customer for a product or service it hasn't fully delivered yet. It's recorded as a liability, not revenue, until the company actually earns it.
A classic example is an annual software subscription paid upfront: the cash arrives in full at signup, but the revenue is recognized gradually over the twelve months the service is actually delivered. Recognizing the full amount as revenue on day one would overstate how much the company has actually earned so far.
Deferred revenue shows up as a liability on the balance sheet precisely because it represents an obligation, service the company still owes the customer, not cash the company is free to treat as earned profit. A company carrying a lot of deferred revenue has real future work ahead of it, which is exactly why investors read that line item closely.
Add your revenue and website for a full diligence brief, reviewed by a CPA who ran EY's West Coast R&D Tax Credit practice for 13 years.