Mam dowód rejestracyjny.

Mam means I have. It is the 1st person singular form of the verb mieć (to have).

So:

• mieć = to have
• mam = I have

This is one of the most common Polish verbs, so it is worth learning early.

In Polish, subject pronouns are often omitted when they are not needed.

The ending of the verb already tells you who the subject is:

• mam = I have
• masz = you have
• ma = he/she/it has

So Mam dowód rejestracyjny already clearly means I have a registration certificate/document without needing ja.

You can say Ja mam dowód rejestracyjny, but that usually adds emphasis, like I do have it or I have it.

It is in the accusative, because it is the direct object of mam.

However, this can be confusing, because for masculine inanimate nouns in Polish, the accusative often looks exactly the same as the nominative.

So:

• dowód rejestracyjny = nominative
• mam dowód rejestracyjny = accusative in function, but the form stays the same

That is why nothing visibly changes here.

Because adjectives in Polish must agree with the noun they describe.

Here, dowód is:

• masculine
• singular
• inanimate

So the adjective also takes the matching form:

• dowód rejestracyjny

Since the accusative of a masculine inanimate noun looks like the nominative, the adjective also stays in the same-looking form here.

Because after an affirmative mam (I have), Polish uses the accusative:

• Mam dowód rejestracyjny.

But with negation, Polish usually uses the genitive:

• Nie mam dowodu rejestracyjnego. = I do not have the registration document.

This is a very important pattern in Polish:

• Mam + accusative
• Nie mam + genitive

Dowód can mean different things depending on context. Its basic sense is proof or evidence.

For example:

• dowód = proof, evidence
• dowód osobisty = ID card
• dowód rejestracyjny = vehicle registration document/certificate

So by itself, dowód does not always mean the same specific document. The full phrase dowód rejestracyjny is what tells you this is the vehicle registration document.

Yes. In normal Polish usage, dowód rejestracyjny refers to the vehicle registration document/certificate, not a general registration receipt or some abstract proof of registration.

So if someone says:

• Proszę pokazać dowód rejestracyjny

they are asking for the official document for the car or other vehicle.

Because Polish has no articles.

English distinguishes between:

• a registration document
• the registration document

Polish usually does not mark that difference with a separate word. Context tells you what is meant.

So Mam dowód rejestracyjny could correspond to:

• I have a registration document
• I have the registration document

depending on the situation.

Yes, Polish word order is more flexible than English word order.

The most neutral version is:

• Mam dowód rejestracyjny.

But other word orders are possible for emphasis, for example:

• Dowód rejestracyjny mam.
  This sounds more marked, as if emphasizing the registration document specifically.

Even though the word order can change, the neutral learner-friendly order here is Mam dowód rejestracyjny.

A simple learner-friendly approximation is:

• mam DO-voot re-ye-stra-TSYJ-nih

A few useful pronunciation notes:

• w sounds like English v
• ó sounds like u
• the final d in dowód is pronounced more like t in actual speech
• the stress in Polish usually falls on the second-to-last syllable
• in rejestracyjny, the stress falls on cyj

So dowód sounds roughly like DO-voot, not like English dowed.

Yes, it is natural and correct, especially as a direct answer to a question.

For example:

• Ma pan dowód rejestracyjny? = Do you have the registration document?
• Tak, mam dowód rejestracyjny. = Yes, I have the registration document.

On its own, it sounds a bit context-dependent, which is normal. It is the kind of sentence you would say when someone asks for the document.

Yes, that is grammatically correct, but it sounds more formal or official.

Compare:

• Mam dowód rejestracyjny. = normal, everyday
• Posiadam dowód rejestracyjny. = more formal, more bureaucratic

In ordinary conversation, mam is much more natural.

You would say:

• Nie mam dowodu rejestracyjnego.

Notice the change:

• Mam dowód rejestracyjny.
• Nie mam dowodu rejestracyjnego.

This happens because negated mieć normally takes the genitive in Polish.

So this is a very useful pair to learn together.