How do you respond to a review you think is from a competitor?

Short answer

Reply professionally as if it's a real customer, note you can't find a matching record, and report it — never accuse the competitor in public. Fake reviews from competitors violate Google's conflict-of-interest policies and can be removed.

Handle it in two moves

• Public: calm and neutral. "We don't have any record of serving you. If you're a real customer, please contact us so we can help." No accusations.
• Private action: flag the review and report it as a policy violation, with any evidence that it isn't a genuine customer.

Accusing a competitor publicly makes you look paranoid to readers and rarely helps. Let the calm reply protect your reputation while Google reviews the report.