Příjem a výdaj patří do stejného zdaňovacího období.

Because the subject is a combination of two nouns: příjem a výdaj = income and expense.

In Czech, just like in English, two singular nouns joined by a (and) usually make a plural subject, so the verb is plural:

• Příjem patří... = The income belongs...
• Příjem a výdaj patří... = Income and expense belong...

So patří is the 3rd person plural form of patřit.

The dictionary form is patřit.

Here are the relevant forms:

• patřit = to belong
• patří = belongs / belong

In this sentence, patří means belong because the subject is plural.

Because patřit do + genitive is a common Czech pattern meaning:

• to belong in
• to fall within
• to be part of

So:

• patřit do období = to belong to a period / to fall within a period

This is especially common when talking about categories, groups, time periods, systems, and classifications.

Compare:

• patřit někomu = to belong to someone
  
  • Ta kniha patří Janovi. = The book belongs to Jan.
• patřit do něčeho = to belong in/within something
  
  • To patří do této skupiny. = That belongs in this group.

Období is in the genitive singular because it follows do.

The preposition do normally requires the genitive:

• do domu = into the house
• do školy = to school
• do období = into / within the period

So in this sentence:

• do stejného zdaňovacího období

the whole phrase after do is in the genitive.

Because období belongs to a neuter noun pattern where the nominative singular and genitive singular look the same.

So:

• nominative singular: období
• genitive singular: období

This can feel strange to English speakers, because the noun itself does not visibly change here. But the case is still clear from:

1. the preposition do
2. the adjective endings: stejného zdaňovacího

Those adjective endings show that the phrase is genitive singular.

Because they must agree with období in:

• case: genitive
• number: singular
• gender: neuter

The base forms are:

• stejný = same
• zdaňovací = tax-, taxable, relating to taxation

In the phrase do stejného zdaňovacího období, both adjectives modify období, so they take genitive singular neuter endings.

A useful point: with adjectives, Czech often makes the case much more visible than the noun does.

It is a fixed tax/accounting term meaning tax period or taxable period.

• zdaňovací comes from zdaňovat = to tax
• období = period

So zdaňovací období is not just any period of time; it specifically means the period used for taxation or tax reporting.

In this context:

• příjem = income, receipt, revenue coming in
• výdaj = expense, expenditure, money going out

These are common accounting and tax words.

A rough way to remember them:

• příjem = money in
• výdaj = money out

Be aware that příjem can have other meanings in other contexts, but here the financial meaning is the one intended.

Czech often uses the singular when talking about a concept in a general or category-like way.

So Příjem a výdaj patří do stejného zdaňovacího období can be understood as something like:

• an income item and an expense item belong to the same tax period
• income and expense belong to the same tax period

If the speaker wanted to emphasize multiple items, they could use plurals such as příjmy a výdaje, but the singular here is completely natural.

No, Czech word order is fairly flexible.

The given sentence is a normal neutral order:

• Příjem a výdaj patří do stejného zdaňovacího období.

You could also say:

• Do stejného zdaňovacího období patří příjem a výdaj.

This version puts more emphasis on the same tax period.

The basic meaning stays the same, but the emphasis shifts.

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

So a Czech noun like příjem can mean, depending on context:

• income
• an income item
• the income

The exact interpretation comes from context, not from an article.

A rough pronunciation guide:

• Příjem ≈ PZHEE-yem
• výdaj ≈ VEE-dye
• patří ≈ PA-tree with Czech ř, which is a special sound
• stejného ≈ STAY-nyeh-ho
• zdaňovacího ≈ ZDA-nyo-va-tsee-ho
• období ≈ OB-doh-bee

The two sounds English speakers often find hardest are:

• ř in patří
• ň in zdaňovacího

Also remember that Czech stress is usually on the first syllable of the word.