The customer is always right was a shop slogan, and the famous get-out is invented

Everything below about the customer is always right comes from what actually happens rather than from what is supposed to.

What the slogan was for

Around the turn of the twentieth century, large department stores were competing to persuade a public accustomed to being cheated by shopkeepers. Selling by fixed price, allowing goods to be examined without obligation and accepting returns were genuine innovations at the time. The slogan was a compact promise that a complaint would be believed rather than argued with, which was the whole selling point.

It is associated with more than one retailer, which is normal for a phrase that spread quickly through an industry. Understood as a returns policy rather than a philosophy of human relations, it was both reasonable and commercially shrewd.

What it was not

It was never a rule that staff must accept abuse, and the retailers using it were perfectly capable of removing people from their premises. It addressed disputes about goods, refunds and service quality, which is a narrow and practical domain.

A returns promise made to a mass market says nothing about how an individual employee should be treated by an individual shopper. The modern use of the phrase to justify unpleasant behaviour is a later extension that the original policy does not support. That extension is a real problem in service work, which is why the correction has been so eagerly received.

The correction that is also wrong

A very widely circulated response holds that the original phrase ended with a clause limiting it to matters of taste. This appears in articles, training material and social media, always confidently and never with a citation to an early source. Nobody has produced an early printed instance containing the extra clause, and the phrase circulated for decades in its short form.

The longer version appears to be a modern improvement, invented because it makes the sentence sensible and gives staff something to point at. It is a good example of a debunking that is more satisfying than the myth and no better supported.

Why invented qualifiers spread

A qualified version of an irritating slogan resolves the irritation, which gives people a strong motive to believe and repeat it. The claim also flatters the person repeating it, since knowing the fuller version implies knowing more than everybody else. Corrections travel faster than verifications, and almost nobody checks a fact that improves a phrase they already disliked.

Tested properly, the same pattern produces invented longer versions of several other famous sayings, always with a clause that reverses the meaning.

When a correction is exactly what you wanted to hear, that is the moment to look for the source.

What the retail history shows

Fixed pricing, marked goods and a returns policy transformed shopping from a negotiation into a transaction, and did so within a generation. Those changes made shops usable by people without the time or confidence to haggle, which expanded the market considerably. Consumer protection law in many countries now provides return and refund rights that no slogan is needed to deliver.

Statutory rights differ substantially between jurisdictions, and a shop policy is generally additional to them rather than instead of them. Knowing which rights are legal and which are goodwill is more useful than any version of the slogan.

A claim being badly sourced does not make its opposite true.

What to keep from all this

The phrase originated as a promise about goods and refunds, and it made sense in that context. Its extension into a general licence for rudeness happened without any support from the people who coined it. The popular fix for that extension is a fabricated clause, and repeating it means correcting a myth with another myth.

The honest version is simply that the slogan was about returns, and never covered how anybody should behave. That statement is less quotable, which is presumably why the invented ending won.

The takeaway

The myth says the customer is always right. The popular correction invents a clause that was never there, which is the better story.

Ask who gained from the claim being repeated. That usually explains the rest.