Dodavatel pošle účet zítra.

Because pošle comes from the perfective verb poslat (to send, as a completed action). In Czech, perfective verbs do not normally have a true present meaning. Their present-form endings are used to express the future.

So:

• posílá = is sending / sends (imperfective, ongoing or habitual)
• pošle = will send (perfective, one completed sending)

That is why Dodavatel pošle účet zítra means The supplier will send the bill/invoice tomorrow.

Both can refer to the future, but they are not used in exactly the same way.

• pošle = perfective, focuses on the action as a single completed event
  
  • He will send it
• bude posílat = imperfective future, focuses more on the process, repetition, or ongoing nature
  
  • He will be sending it / He will send it repeatedly

In this sentence, the idea is a single future act: sending the bill tomorrow. So pošle is the natural choice.

Dodavatel is in the nominative singular, which is the normal case for the subject of the sentence.

You can tell it is the subject because:

• it is in the nominative form
• the verb pošle is 3rd person singular, matching dodavatel
• semantically, the supplier is the one doing the action

So:

• dodavatel = the supplier (subject)
• pošle = will send
• účet = the thing being sent

Here účet is in the accusative singular, because it is the direct object of the verb pošle.

The tricky part is that for this noun, the nominative and accusative forms look the same:

• nominative: účet
• accusative: účet

That is normal for many masculine inanimate nouns in Czech.

So even though the form does not change, its role in the sentence is clear from the structure: it is the thing being sent.

It can mean different things depending on context:

• bill
• invoice
• account

In a sentence with dodavatel (supplier), the most natural meaning is usually invoice or bill, because a supplier typically sends an invoice.

So the exact English word depends on context, even though the Czech word is the same.

Czech does not have articles like English a/an and the.

So dodavatel can mean:

• a supplier
• the supplier

And účet can mean:

• a bill / an invoice
• the bill / the invoice

Which one sounds best in English depends on the context. Czech leaves that information unstated unless something else makes it clear.

Yes. Czech word order is quite flexible because case endings help show who is doing what.

The neutral order here is:

• Dodavatel pošle účet zítra.

But you could also say things like:

• Zítra pošle dodavatel účet.
• Účet pošle dodavatel zítra.
• Dodavatel zítra pošle účet.

These versions all keep roughly the same basic meaning, but the focus or emphasis changes.

For example:

• starting with Zítra emphasizes tomorrow
• starting with Účet emphasizes the bill/invoice

So the original sentence is a normal, neutral way to say it.

Because zítra is an adverb meaning tomorrow. It works by itself, just like English tomorrow.

So:

• zítra = tomorrow
• not v zítra

This is completely normal in Czech. Many time expressions work without a preposition:

• dnes = today
• zítra = tomorrow
• včera = yesterday

A simple approximate pronunciation is:

• Dodavatel → DO-da-va-tel
• pošle → PO-shle
• účet → OO-chet
• zítra → ZEE-tra

A few useful notes:

• Czech stress is usually on the first syllable: DOdavatel, POšle, Účet, ZÍtra
• š sounds like English sh
• č sounds like English ch in check
• í and ú are long vowels

Not really in normal Czech usage. Because pošle is from a perfective verb, it naturally points to a future completed action.

So Czech speakers understand:

• pošle = will send

If you wanted a present or habitual sense such as sends, you would normally use the imperfective verb:

• Dodavatel posílá účet. = The supplier is sending / sends the bill
• Dodavatel posílá účty každý měsíc. = The supplier sends invoices every month

So in your sentence, pošle strongly signals the future.

Dodavatel is a masculine noun form. It is often used in a general or unspecified way, especially in business language.

If you specifically want to say a female supplier, Czech can use:

• dodavatelka

But in many business or formal contexts, the masculine form may still be used generically when the person’s gender is not the focus.

So in this sentence, dodavatel is simply the standard dictionary form meaning supplier.