What is back translation?

Occasionally, a language services client needs an additional validation step called a “back translation.” Back translation is the translation of a target document back to the original source language. The process guards against potentially lethal mistakes in specialized, technical and medical materials.

Who requires it?

A back translation adds an additional layer of quality assurance for sensitive or high risk information. Institutional Review Boards (IRBs) and ethics committees often require this process for translations of research surveys and clinical trials. Regulatory agencies might require proof of accuracy for translations of instructions for medical devices and potentially dangerous industrial processes. Back translation helps identify any ambiguities or sensitive details in the source. It also assures that any cross-cultural misunderstandings are addressed before publication of the translated text.

What should you expect?

A separate linguist with no knowledge of the original source content should translate the target document back into the source language. It won’t be an exact replica of the original source text. There is no mathematical formula for translation, and one translator’s word choice can never exactly match another’s. We instruct our linguists to translate as literally and comprehensively as possible, using precise dictionary terms, while avoiding personal stylistic choices. When the target has been translated back into the source language, the reconciliation process begins.

How does the reconciliation process work?

We compare the back translation to the source text to flag any areas where concepts might diverge. We then pass the reconciliation report to the client’s editorial team for input.

If there are substantial differences between the original source text and the translation of the target, the original translator addresses any ambiguities or inconsistencies. The translator will provide feedback by either defending their translation or offering an alternative that best expresses the content in the client’s original source text. Substantial differences are reconciled by either correcting the target translation or clarifying the ambiguities in the source.

Guidelines for clients

Reconciliation is not an exact science. The following guidelines can help to ensure a speedy and efficient reconciliation process.

Don’t contract with a separate company

You should use the same language partner when translating back to the source language that you used for your original translation. (The exception is when the original translation was done by an individual translator. You do not want the same person doing both steps). An ISO 17100-certified language partner will guarantee that this quality assurance step is performed by a second professional team with no knowledge of the original source text. Using professionals minimizes “false positives” (errors in the back translation itself) for a cost-effective reconciliation process. Furthermore, no language service provider can provide a certificate of accuracy for translations they did not perform. If you need to submit a certificate of accuracy, don’t switch providers.

Leave linguistic details to the translation team

Word order and grammatical conventions may not be exactly the same in the target language. Suggesting that words be rearranged in the translation to exactly match the target (for example, a preference for passive voice instead of active voice) may lower the quality of the translation or be grammatically incorrect in the target language.

Don’t panic if the source doesn’t match exactly

If you find a discrepancy, wait for the translation team to review your comments and provide you with feedback before demanding a revision. It does not mean that the translation is incorrect, only that it should be reviewed.

  • A word or phrase in the translation may have multiple meanings. For example, in a translation into Spanish, a medical translator used the term “girar” to indicate a “swinging” motion. The back translator used the word “twist.” “Girar” can translate as “twist,” “swing,” or “turn,” and thus, “girar” is, in fact, an appropriate translation. In this case, the translation was flagged as a potential error but was eventually defended by the translator and retained in the target document.
  • An error could have been introduced by the back translator. We all make mistakes sometimes.
  • The final possibility is that the original translation did not stay true to your message in some respect and must be revised. That’s what we’re here for!

Not all differences matter

Sentence structure and word choice are not important if the meaning of the content is the same. Focus on the underlying meaning. Don’t try to force changes in the translation so that the back translation will be a word-for-word equivalent of the source.

Example of a difference that matters (from a health insurance claim):

Original English source textinflammation
English to Arabic translationإلتهاب
Arabic back into Englishinfection

From a medical standpoint, inflammation and infection are entirely different concepts and such a discrepancy may cause confusion on a health insurance claim. This is a case where the translator should revise the translation, providing more detail and clarity.

Example of a difference that doesn’t matter:

Original English source textwaste
English to German translationAbfall
German back into Englishtrash

In this case, “waste” and “trash” are synonyms. The distinction between the two terms is not critical for readers of this particular text. This is not a case where a revision is necessary for conveying the meaning of the source text.

The source documents may be unclear

Always provide your translation partner with an edited, finalized source document for translation. Even when you think your document is 100% ready for translation, translating t back may reveal an ambiguity in the original source text, which may itself require revision. For example:

Original English source textThe approved documents and contracts were submitted to the lawyer.
English to Spanish translationLos documentos aprobados y los contratos se presentaron al abogado.
Spanish back into EnglishThe approved documents and the contracts were submitted to the lawyer.

Were both the legal documents AND the contracts approved? Or the legal documents only? Looking at the English source, it is not clear. This is a case where a source revision may be necessary.


Back translation can be a valuable validation check when accuracy is critically important. Following the above suggestions will help the process go smoothly. This process is best suited for checking technical and medical content. To assess subjective matters of style or branding, we recommend review by a member of the client’s in-country team instead.