An addendum is an appendix with which information is added to a writing, document, contract, book or manual. The word, as such, comes from the Latin addenda, which means ‘what has to be added’, which in turn comes from the verb addeĕre, which means ‘add’.
Thus, the term is mainly used in reference to written productions to which, for one reason or another, it has been necessary to add modifications, corrections or extensions of what is contained in the main text.
In this sense, the addendum can be both a supplementary addition and an appendix to the main work.
We can find addenda in books, in the style of an erratum, to make corrections without reprinting the entire print run; in legal contracts, to include with modifications on the original document; in research, to add or expand relevant information that was obtained once the work was completed; in medical writings, to add some new information that may be useful for the treatment of the patient, among other cases.
It should also be noted that the word adenda may appear used in its Latin spelling addendum, and, consequently, also in its plural form addenda.
Addendum in a contract
In a contractual deed, an addendum is an appendix that is added to the contract in order to modify, extend or specify the terms of the obligations incurred, without the need to write a new document.
Addenda, in this sense, are used to make changes or add specific details. An addendum, for example, could set prices or define a date for the delivery of a good.
It is also commonly used that the addendum refers to the contract or, conversely, that the contract refers to the addendum. The purpose of this is to indicate, explicitly, that the document contains a modification introduced by an addendum.
Addendum in electronic invoices
In electronic invoicing, it is known as an addendum that provides additional information to that included in the electronic invoice.
In this sense, in the addendum you can include data of great value for the company and the knowledge of the business, such as, for example, who sold a product, its code or the purchase number. In addition, the format of the addendum does not have to be rigid, as it does not contain fiscal data.
Addenda in electronic invoices are a billing method adopted in Mexico and allowed by the SAT (or Tax Administration Service, for its acronym).