Translation of "IOU"

Question

I wish to know the Portuguese for "IOU". I.e. an informal note someone may write on a piece of paper to acknowledge that they owe someone something. It appears impossible to search for it in online dictionaries because IOU isn't a word and if I searched for "I owe you" I am concerned that the answer might not be the same thing.

I also want to be sure that it really means the same thing, so for example I don't want a technical term that only economists or bankers would use.

Answer 1

An IOU is a word. It's on Wikipedia:

IOU

A palavra quer dizer e se traduz por (um) reconhecimento de dívida

Não há outra tradução.

• O reconhecimento de dívida designa a declaração unilateral mediante a qual alguém reconhece uma dívida a outrem.

Lexionário

An IOU can be something official between companies, say, or just a paper I write and sign, saying I owe someone money. It is not a negotiable instruments. The negotiable debt instrument is called a promissory note, nota promissória.

Answer 2

TL;DR — I'd suggest: "declaração (or nota) de dívida" for pt-BR.

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The OP is explicitly about pt-PT and is already answered in Lambie's post, but it seems to make more sense to address here too the translation to pt-BR than to have a separate question for it.

It's difficult to find a good translation, since the exact concept is not used in Brazilian Portuguese.

The most immediate translation could seem to be "nota promissória", but this is "promissory note", a more formal, negotiable instrument, as Lambie's answer explains. One could perhaps consider an IOU as an informal promissory note, what suggests the translation "nota promissória informal" — which is correct enough and understandable, but has the big disadvantage of never being used in practice (as Google's 6 hits attests).

Translation suggestions include "título de dívida", "vale", "recibo, and "adiantamento", none of which really works: "título de dívida" is "debt security", "debenture" or other financial asset; " "vale" is rather "coupon" or "voucher", thus a IOU of sorts, but only in specific, usually commercial contexts; "recibo is "receipt" and thus too general; and "adiantamento" is actually unrelated, meaning things such as "retainer" or "advance".

So we're left with using a description for a translation, such as, for pt-PT, "reconhecimento de dívida" ("acknowledgment of debt") or, for pt-BR, "declaração de dívida" ("statement or declaration of debt"). Notice that "reconhecimento de dívida" doesn't work so well in pt-BR because in Brazil this expression refers to a specific government issued document.