I dati anagrafici devono essere corretti.

I is the masculine plural definite article in Italian, equivalent to the in English.

Here it goes with dati, which is a masculine plural noun:

• il dato = the datum / the piece of data
• i dati = the data

So i dati means the data.

Because the sentence is talking about more than one piece of information, so Italian uses the plural form.

• dato = singular
• dati = plural

Since anagrafici and corretti describe dati, they also have to be plural.

In this context, anagrafici refers to personal details / personal data / registration details, such as:

• name
• date of birth
• address
• tax or identification information

It comes from anagrafe, which is the official civil registry. So dati anagrafici is a very common fixed expression in Italian for personal details.

Because it is an adjective describing dati, and Italian adjectives usually must agree with the noun they describe in:

• gender
• number

Since dati is masculine plural, the adjective must also be masculine plural:

• dato anagrafico = singular
• dati anagrafici = plural

Because the subject is i dati anagrafici, which is plural.

The verb dovere must agree with the subject:

• deve = he/she/it must
• devono = they must

So:

• Il dato anagrafico deve essere corretto = The personal detail must be correct
• I dati anagrafici devono essere corretti = The personal details must be correct

Devono essere is a very common Italian structure:

• devono = must
• essere = be

Together, dovere + infinitive means must + verb.

So:

• devono essere = must be

Other examples:

• I documenti devono essere firmati = The documents must be signed
• Le informazioni devono essere aggiornate = The information/details must be updated

Corretti is the adjective correct in the masculine plural form.

It agrees with dati:

• dato corretto = correct datum / correct piece of data
• dati corretti = correct data

In the sentence, corretti comes after essere, so it functions like a predicate adjective:

• I dati sono corretti = The data are correct
• I dati devono essere corretti = The data must be correct

It can look like both, because many Italian past participles are also used as adjectives.

Here, learners usually understand it best as an adjective meaning correct.

So the sentence means that the data need to be correct, not necessarily that someone must correct them.

If Italian wanted to clearly express must be corrected, context would usually make that meaning obvious, but devono essere corretti can sometimes be ambiguous out of context.

In Italian, most descriptive adjectives normally come after the noun.

So:

• dati anagrafici = personal details

Putting anagrafici before the noun would sound unnatural here. This expression is basically a standard set phrase in Italian.

Yes, but the meaning changes slightly.

• I dati anagrafici sono corretti = The personal details are correct
• I dati anagrafici devono essere corretti = The personal details must be correct

So sono states a fact, while devono essere expresses a requirement or necessity.

In standard Italian, dato is singular and dati is plural.

So Italian normally treats dati as plural:

• I dati sono...
• I dati devono...

English can be less consistent with data, but Italian is much more straightforward here: dati is plural.

Yes, exactly.

That is the singular version:

• Il dato anagrafico deve essere corretto = The personal detail must be correct

Notice how everything changes to singular masculine:

• il
• dato
• anagrafico
• deve
• corretto

Yes, it is fairly formal and very common in:

• forms
• official documents
• websites
• administrative language
• customer service contexts

In everyday speech, people might sometimes say things like:

• i tuoi dati
• i dati personali
• le informazioni personali

But dati anagrafici is especially common when referring to official personal details.

The pattern is:

article + noun + adjective + modal verb + infinitive + adjective

More specifically:

• I = the
• dati = data/details
• anagrafici = personal/registry-related
• devono = must
• essere = be
• corretti = correct

So the structure is:

The personal details must be correct.

This is a very useful model for many Italian sentences, for example:

• I documenti devono essere completi = The documents must be complete
• Le informazioni devono essere precise = The information must be accurate
• I moduli devono essere firmati = The forms must be signed