What it means
In footnotes and citations, idem avoids repeating an author's name. If a document cites a paper by one author and then another work by the same author, the second reference may use idem in place of the name.
Style guides differ on how to use it, and many modern guides prefer repeating the name or using a short form. In law, idem appears in phrases and documents where one item is "the same as" another.
A contract might refer to a prior clause and then to idem to mean that the same conditions apply. Lawyers also use related Latin terms, such as "ibid." and "supra", so the vocabulary can be bewildering for non-specialists.
In finance and accounting, the word is most likely to appear in older documents, annual report notes, legal agreements and academic papers. For example, a note might say that the accounting treatment for one class of assets is idem for another, meaning the same rule applies.
Auditors' working papers may also use it as shorthand for "same as above". Because it is a specialist and slightly old-fashioned term, plain English is usually better in business writing.
Phrases such as "the same author", "the same clause" or "as above" are clearer to a general reader and avoid confusion. If a document does use idem, the reader should check what it points back to.
The word should not be confused with ibid., which comes from the Latin ibidem and means "in the same place". Ibid. refers to the same source and often the same page, while idem refers to the same author or thing.
Mixing them up is a common error in academic and legal citations. Finance professionals who read research papers, regulations or old legal agreements will meet the term from time to time.
A quick check of the previous citation or clause normally resolves any doubt. If the meaning is still unclear, asking the author or a lawyer is better than guessing.
In practice
Real-world examples.
Example
A footnote in an academic paper cites a study by a well-known economist and then cites a second study by the same economist as "idem, 2009". The reader understands the author is unchanged, although some readers must pause to recall the Latin.
Example
A legal agreement sets out the notice period for terminating a supply contract and then states that the same period applies to a related licence, using "idem" to refer back. The finance team checks the earlier clause to confirm the number of days. They then diarise the date in the contract tracker so that no deadline is missed.
Example
An auditor reviewing a schedule of 40 invoices ticks the first ten with a note of the checks performed and writes "idem" against the next 30, meaning the same checks were done. A reviewer can follow the trail easily, provided the firm's methodology states what the shorthand covers.
Case study
Seen in the real world.
Calder and Ward is an illustrative, fictional audit firm whose manager, Imogen, was reviewing the working papers of a junior colleague. The papers recorded the checks on sales invoices for a client with annual revenue of $12,000,000. The sample covered 60 invoices chosen across all months of the year.
For the first invoice, the junior had described each step in detail. For the next 25 items he had written only "idem" next to the amounts, which Imogen could not be sure meant that all steps had been repeated.
In this illustrative story she asked him to replace "idem" with a short list of ticked steps, and the firm updated its template so that every reviewer could see what was done. The lesson is that shorthand saves time only when everyone reads it the same way, and clarity matters more than brevity in documentation. A reviewer who has to guess what was done cannot rely on the work.
Watch out
Common mistakes.
- Confusing idem with ibid., when idem means the same author or thing and ibid. means the same place or source.
- Using Latin shorthand with readers who may not recognise it, when plain English is clearer.
- Using idem without making clear what it refers to, which can cause confusion in contracts and audit papers and may cause disputes about what was meant.
Questions
People also ask.
What does idem mean?
It means "the same" in Latin and is used to refer to something already mentioned, such as the same author, clause or checking procedure.
Is idem still used?
It appears in some legal, academic and older business documents, but many style guides now prefer plain English because modern readers may not recognise the Latin.
What is the difference between idem and ibid.?
Idem refers to the same author or item, while ibid. points to the same source, often with the same page.
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