What is a single source of truth?
A single source of truth is the designated system or table that holds the authoritative version of a particular piece of information, which every other system and report either reads from or copies without altering. The concept applies per data element rather than to the company as a whole. The human resources system is the source of truth for who is employed and in which department; the ERP is the source for inventory on hand. Other systems may hold copies for speed or convenience, but when copies disagree, the designated source wins.
Why a single source of truth matters
Without a designated source, every disagreement between two reports becomes an investigation, and people stop trusting all of them. A professional services firm counted headcount three ways, because payroll, the staff directory, and the project management tool each removed leavers on a different schedule. Naming the HR system as the source and feeding the others from it ended the argument. For AI, the principle decides what an agent may read. A client balance comes from the receivables ledger that finance stands behind, with master data management keeping customer identifiers aligned across systems.
What to watch for
- Name the source of truth for each important entity in writing, including who may change it.
- Make copies read-only or clearly labeled as copies, because edits made to a copy are the usual way disagreement returns.
- Aim for one source per data element rather than one system for everything.