Dnes je nutné podat daňové přiznání.

Because dnes means today, and Czech often puts time expressions near the beginning of the sentence.

So:

• Dnes je nutné podat daňové přiznání. = Today it is necessary to submit a tax return.

This word order sounds natural and highlights when the obligation applies.

Other word orders are possible, for example:

• Je nutné dnes podat daňové přiznání.

But the original version is very normal and straightforward.

Je nutné means it is necessary.

Breakdown:

• je = is
• nutné = necessary

This is a very common Czech impersonal structure:

• je nutné + infinitive
• je třeba + infinitive
• je možné + infinitive

Examples:

• Je nutné čekat. = It is necessary to wait.
• Je možné odejít. = It is possible to leave.

In English, we often use it as a dummy subject: It is necessary...
Czech does not need a word for that it here.

Because this is an impersonal construction.

In je nutné podat daňové přiznání, the idea expressed by the infinitive phrase (to submit a tax return) functions like the thing that is necessary. Czech commonly uses the neuter singular form of the adjective in this kind of sentence.

So:

• nutný = masculine
• nutná = feminine
• nutné = neuter / impersonal predicative use

This is similar to:

• Je jasné, že... = It is clear that...
• Je důležité učit se. = It is important to study.

Because it depends on je nutné.

The pattern is:

• je nutné + infinitive = it is necessary to ...

So:

• podat = to submit / to file

The sentence literally works like:

• Today is necessary to submit a tax return

More natural English:

• Today it is necessary to submit a tax return.

So the infinitive is used because the sentence is talking about an action in general, not conjugating that action for a specific person.

Because Czech often uses impersonal expressions when the obligation is general or obvious from context.

This sentence does not directly say:

• I must submit
• you must submit
• we must submit

Instead, it says something like:

• Submitting a tax return is necessary today.

This style is common in official, formal, and administrative language. It sounds more neutral and less personal than:

• Musíte podat daňové přiznání. = You must submit a tax return.

Because daňové přiznání is the direct object of podat.

The verb podat takes the accusative case, and daňové přiznání is in the accusative.

In this phrase:

• přiznání is a neuter noun
• daňové is the adjective agreeing with it

Important detail: for neuter nouns like přiznání, the nominative and accusative forms are often the same, so you do not see a visible change here.

So although the form looks unchanged, it is still functioning as an accusative object.

Literally, it is:

• daňové = tax-related / tax
• přiznání = declaration / statement

Together:

• daňové přiznání = tax return / tax declaration

This is the standard Czech term for a tax return.

Because podat is the normal verb used in Czech for formally submitting documents, applications, returns, complaints, etc.

Common combinations include:

• podat žádost = submit an application
• podat přihlášku = submit an application / registration
• podat daňové přiznání = file/submit a tax return

So podat is idiomatic here. It is the verb Czech speakers naturally use with this kind of formal document.

Yes, podat is perfective.

Its imperfective partner is podávat.

Very roughly:

• podat = submit / file as a completed act
• podávat = be submitting / submit repeatedly / be in the process of submitting

In this sentence, podat makes sense because the point is that the tax return must be filed/completed by today.

Compare:

• Dnes je nutné podat daňové přiznání.
  = Today it is necessary to file the tax return.

If you used podávat, it would usually sound less natural here unless the context specifically focused on an ongoing or repeated process.

Yes, it sounds fairly formal and somewhat administrative.

That is very natural for topics like taxes, deadlines, and official obligations.

A more conversational version might be:

• Dnes musíte podat daňové přiznání. = You have to file your tax return today.
• Dnes se musí podat daňové přiznání. = The tax return has to be filed today.

But the original sentence is perfectly normal, especially in written notices or official contexts.

Yes. That is a very common alternative.

• Je nutné = it is necessary
• Je třeba = it is necessary / it is needed / one must

So:

• Dnes je třeba podat daňové přiznání.

has almost the same meaning.

Both are correct.
Je třeba is extremely common in Czech and often sounds a little less stiff than je nutné, though both are standard.

A few useful pronunciation points:

• daňové: the ň is a soft n sound, somewhat like the ny in canyon
• ř in přiznání is the famous Czech sound: a raised, vibrating r-like sound
• á is long, so in -nání the vowel is held a bit longer

Very rough pronunciation guide:

• daňové ≈ dan-yo-veh
• přiznání ≈ przhi-znaa-nee

The hardest part is usually ř. If you cannot say it perfectly yet, an approximation is fine at first.

Yes, depending on context.

Czech has no articles, so daňové přiznání could correspond to:

• a tax return
• the tax return
• sometimes even your tax return

The exact English choice depends on context.

In a general instruction, English often uses:

• Today you must file your tax return.
• Today it is necessary to file a tax return.

So the Czech sentence itself does not explicitly mark definiteness the way English does.