What Is a Backlog?
A backlog is the value of orders a company has received and accepted but has not yet filled. Companies that build products, run projects, or sell long-term contracts often carry a backlog, since customers commit before the work is finished. Backlog is most common in industries such as aerospace, construction, and heavy equipment, where production and project timelines are long. It is usually expressed as a dollar amount and reported in company filings, earnings releases, or investor presentations.
How It Works
When a customer signs a contract or places a firm order, the company adds that value to its backlog. As the company delivers the product or completes the work, it reduces the backlog and records the matching revenue recognition in its financial statements. Orders that are canceled or changed are removed or adjusted. Because of this, backlog rises when new orders arrive and falls when work is completed.
Some companies pair backlog with a book-to-bill ratio, which compares orders received to revenue billed over a period. A ratio above one suggests orders are growing faster than sales. Payments received in advance may appear separately as deferred revenue, which is a related but distinct balance sheet item.
Why It Matters to Investors
Backlog can offer a view of future sales that current revenue does not show. A growing backlog may suggest demand is strong, while a shrinking one may signal slowing business. Investors often compare backlog over several quarters and read management commentary alongside it, including any earnings guidance the company provides.
Limitations
Backlog is not a guarantee of revenue. Contracts can be delayed, reduced, or canceled, and definitions differ between companies, so one firm's backlog may not be directly comparable to another's. Investors should check how a company defines backlog in its filings. Backlog also says nothing about gross margin or profitability, so it is generally treated as one input among several rather than a complete measure of performance.
Updated October 23, 2026. For general education only; not financial, tax or legal advice.