Pronajímatel musí doložit náklady.

The base form is muset = to have to / must.

Musí is the 3rd person singular present tense form, because the subject is pronajímatel (the landlord / lessor), which is singular.

A quick mini-pattern:

• musím = I must
• musíš = you must
• musí = he/she/it must, and also they must in some contexts

So:

• Pronajímatel musí... = The landlord must...

Because after muset (must / have to), Czech normally uses an infinitive:

• musí doložit = must provide / must substantiate
• musí zaplatit = must pay
• musí přijít = must come

This is very similar to English must + verb.

So the structure is:

subject + musí + infinitive + object

In this sentence:

• Pronajímatel = subject
• musí = must
• doložit = infinitive verb
• náklady = object

Doložit usually means something like:

• to document
• to provide proof of
• to substantiate
• to support with evidence

So in legal, administrative, or housing contexts, doložit náklady usually means:

• to provide documents showing the costs
• to prove the expenses with evidence

It is a bit more formal than just ukázat (to show).

This is a question of aspect, which is very important in Czech.

• doložit = perfective
• dokládat = imperfective

Here, doložit suggests a completed result: the landlord must submit / prove / document the costs successfully.

That fits well with obligations:

• musí doložit = must provide the documentation / must substantiate it

If you used dokládat, it would sound more like an ongoing, repeated, or process-oriented action:

• musí dokládat náklady = must keep documenting the costs / must document the costs repeatedly

So doložit is the natural choice if the idea is a specific required act with a clear outcome.

Náklady is the accusative plural of náklad.

Here it is the direct object of doložit, so accusative is required.

Singular:

• náklad = cost / expense

Plural:

• náklady = costs / expenses

For many masculine inanimate nouns, the nominative plural and accusative plural are the same, so:

• nominative plural: náklady
• accusative plural: náklady

That is why the form does not visibly change here.

In this kind of context, plural is very natural because it usually refers to expenses / costs as a set of items.

• náklady = costs / expenses

The singular náklad exists, but it often means:

• a single cost item
• a load / cargo in other contexts

So in legal or financial language, náklady is the normal choice when talking about expenses generally.

Pronajímatel literally means the one who rents something out / lessor.

In housing contexts, it is usually best translated as:

• landlord

But more generally it can also mean:

• lessor
• person or company renting something out

It comes from the verb pronajímat (si / něco), related to renting out.

A useful contrast:

• pronajímatel = landlord / lessor
• nájemce = tenant / lessee

So this sentence is clearly talking about the person on the owner/renter-out side, not the tenant.

Because Czech has no articles.

English says:

• the landlord
• a landlord

Czech simply says:

• pronajímatel

Whether it means the landlord, a landlord, or landlords in general depends on context.

In this sentence, English would usually translate it as the landlord must... because the situation probably refers to a specific landlord already known from the context.

The given order is the most neutral one:

Pronajímatel musí doložit náklady.

Czech word order is fairly flexible, and changes are often about emphasis rather than basic grammar.

For example:

• Náklady musí pronajímatel doložit.
  = It is the costs that the landlord must document.

• Musí pronajímatel doložit náklady?
  = Must the landlord document the costs?

So yes, it can change, but the original sentence is the standard neutral order for a plain statement.

A rough pronunciation guide is:

proh-NAH-yee-mah-tel MOO-shee DOH-loh-zhit NAA-klah-dih

A few key sounds:

• pronajímatel: stress on the first syllable in Czech, even though English speakers often want to stress a later one
• musí: š sounds like sh
• doložit: ž sounds like the s in measure
• náklady: long á, so the first vowel is held a bit longer

Important note: Czech stress is almost always on the first syllable of the word.

Yes, depending on context, that could be a reasonable translation.

Because doložit náklady is about supporting costs with evidence, possible English renderings include:

• The landlord must document the costs.
• The landlord must provide proof of the costs.
• The landlord must substantiate the expenses.
• The landlord must itemize and document the costs. (if the context suggests a detailed breakdown)

The exact English choice depends on whether the focus is on:

• proof,
• paperwork,
• supporting documents,
• or a detailed breakdown.

Yes, it sounds fairly formal or administrative/legal.

Words like:

• pronajímatel
• doložit
• náklady

are very common in contracts, regulations, official letters, and housing law.

In casual speech, people might still say it, but in everyday conversation they might also choose simpler wording depending on the situation.