A fake one-star review makes you want to reply immediately. Pause for a moment. First, check whether it can be removed.
First: check whether it is fake
Look at the reviewer's profile. Is the customer missing from your orders, calendar and customer list? Does the review describe a service you do not offer? It is probably not from a customer. A review you simply disagree with is not fake and cannot be removed for that reason.
Report the review to Google
Sign in to Google Business Profile, open Reviews and report the review as a policy violation. Only reviews that break Google's rules can be removed. You cannot delete them yourself. Take a screenshot and record the date and why you believe it is fake. Google may not remove it, and reports are often rejected. It is still worth trying before you reply.
If someone demands money to remove reviews
A sudden series of one- and two-star reviews followed by a demand for money or services to remove them is extortion. Collect screenshots of the messages and report it using Google's dedicated form.
If it stays: keep your reply brief and factual
After reporting, you can reply. Keep it short and calm, without arguing. For example, explain that you cannot find a customer with that name and would welcome further details. Future customers will read your reply, not just the reviewer.
What helps most over time
More genuine customer reviews make a single fake one less prominent. Ask your customers after each job.
Not sure whether the review can be removed? Contact us and we can look at it with you.