No tengo ninguna duda sobre el informe.

In Spanish, subject pronouns are often omitted because the verb ending already shows who the subject is. Tengo clearly means I have, so yo is not necessary.

You could say Yo no tengo ninguna duda sobre el informe, but adding yo usually gives extra emphasis, contrast, or clarity. In a neutral sentence, leaving it out sounds more natural.

Spanish normally uses double negatives, unlike standard English.

So:

• No tengo ninguna duda = literally I do not have no doubt, but in correct Spanish this means I have no doubt
• The no goes before the verb
• Ninguna reinforces the negative idea

If you remove no, the sentence becomes ungrammatical in standard Spanish:

• Tengo ninguna duda is not correct

Ninguna means no, not any, or not a single in this context.

It is feminine singular because it agrees with duda, which is a feminine singular noun:

• ninguna duda
• ningún problema

So the form changes depending on the noun:

• ningún
  • masculine singular noun
• ninguna
  • feminine singular noun

Spanish often uses a singular noun after ningún/ninguna when English might use either singular or plural.

So:

• No tengo ninguna duda = I have no doubt
• Literally: I do not have not-even-one doubt

Using the singular emphasizes the idea of not a single doubt. This is the normal and idiomatic way to say it.

Yes. No tengo dudas is also correct and natural.

There is a slight nuance:

• No tengo ninguna duda sounds a bit stronger or more emphatic: I have absolutely no doubt
• No tengo dudas simply means I have no doubts

Both are common, but ninguna adds emphasis.

Yes, both can be possible, but they are not always exactly the same in feel.

• sobre el informe = about/regarding the report
• del informe can also mean about the report, especially after duda

With duda, Spanish commonly uses both sobre and de:

• No tengo ninguna duda sobre el informe
• No tengo ninguna duda del informe

However, many speakers may prefer:

• No tengo ninguna duda sobre el informe when meaning regarding the report
• No tengo ninguna duda de que... when followed by a clause, for example: No tengo ninguna duda de que es correcto

So sobre is very natural here for about/regarding.

Spanish uses definite articles more often than English.

Here, el informe means the report, referring to a specific report already known in the conversation or context.

If you said sobre un informe, that would mean about a report, not a specific one.

Tengo is the first person singular present indicative of tener.

So:

• tengo = I have

It is used here for a present state:

• No tengo ninguna duda = I have no doubt

Yes, tener dudas or tener duda is a very common way to express doubt.

Examples:

• Tengo dudas = I have doubts
• No tengo ninguna duda = I have no doubt

Spanish can also use the verb dudar:

• Dudo del informe = I doubt the report
• No dudo del informe = I do not doubt the report

But in your sentence, the structure with tener is completely natural.

Not in this sentence.

With a noun, ninguna goes directly before that noun:

• ninguna duda

The negative structure is:

• no
  • verb + ninguna
    • noun

So:

• No tengo ninguna duda ✅
• Ninguna tengo duda ❌

There is a different structure where ninguno/ninguna can act as a pronoun:

• No tengo ninguna = I don’t have any But that is not what is happening in your sentence.

The normal order is:

• No tengo ninguna duda sobre el informe

Spanish word order is flexible, but this neutral order is the most natural.

You might change the order for emphasis:

• Sobre el informe no tengo ninguna duda This puts extra focus on sobre el informe, as if contrasting it with something else.

But for everyday use, the original order is best.

The personal a is only used before specific people or sometimes personified beings, not ordinary things.

Since el informe is a thing, not a person, there is no a:

• sobre el informe ✅
• sobre al informe ❌

A natural pronunciation in connected speech will often soften the boundaries between words.

A rough guide:

• ninguna duda → something like neen-GOO-na DOO-tha in much of Spain
• In many parts of Spain, d between vowels can sound softer, so duda may sound a bit like DHU-tha
• In most of Spain, z and soft c have a th sound, but here there is no z/c in duda; the th-like effect learners sometimes notice comes from the soft d, not from spelling

The stress is:

• ninGUna
• DUda

Yes, that is a very good natural translation in many contexts.

Because of ninguna, the sentence can sound a bit stronger than just I have no doubt. Depending on tone and context, it may suggest:

• I have no doubt about the report
• I have absolutely no doubt about the report
• I don’t have a single doubt about the report

So if you want to reflect the emphasis of ninguna, adding absolutely in English can work well.