Налоговая база зависит от налогооблагаемого дохода.

Налоговая база is the subject of the sentence, so it is in the nominative case.

• база = base
• налоговая = tax, tax-related

Because база is a feminine singular noun, the adjective must match it:

• налоговая = feminine singular nominative
• база = feminine singular nominative

So налоговая база is a matching adjective + noun phrase in the nominative.

The verb зависит is the 3rd person singular form of зависеть (to depend).

It is singular because the subject is налоговая база, which is one thing:

• я завишу = I depend
• ты зависишь = you depend
• он / она / оно зависит = he / she / it depends
• они зависят = they depend

Since налоговая база is singular, Russian uses зависит.

In Russian, the verb зависеть is normally used with the preposition от, and together they mean to depend on.

So the pattern is:

зависеть от + genitive

Examples:

• зависеть от погоды = to depend on the weather
• зависеть от цены = to depend on the price
• зависеть от дохода = to depend on income

So in your sentence, от is not optional. It is part of the normal construction of the verb.

Because the preposition от requires the genitive case.

The basic form is:

• доход = income (nominative)

After от, it changes to the genitive:

• от дохода = on/from income, depending on income

So:

• зависит от дохода = depends on income

This is one of the most important things to memorize: many Russian prepositions force a specific case, and от takes the genitive.

Налогооблагаемого is the adjective налогооблагаемый in the genitive singular masculine form.

Why that form?

Because it describes дохода, and adjectives in Russian must agree with the noun in:

• gender
• number
• case

Here the noun is:

• доход = masculine
• singular
• genitive after от

So the adjective must also be:

• masculine
• singular
• genitive

That gives:

• налогооблагаемый доход = taxable income
• от налогооблагаемого дохода = on taxable income / from taxable income, depending on taxable income

The dictionary form is налогооблагаемый.

That is the masculine singular nominative form, which is the standard form dictionaries use for adjectives.

Some forms of this adjective are:

• налогооблагаемый доход = taxable income
• налогооблагаемая база = taxable base
• налогооблагаемое имущество = taxable property
• налогооблагаемые суммы = taxable amounts

In your sentence, it becomes налогооблагаемого because it has to match дохода in the genitive singular masculine.

Yes, both are related to tax, but they mean different things.

• налоговый / налоговая / налоговое = tax, tax-related
• налогооблагаемый = taxable, subject to tax

So:

• налоговая база = tax base
• налогооблагаемый доход = taxable income

A useful way to think about it:

• налоговая describes something connected with the tax system
• налогооблагаемый describes something that is actually taxed

The neutral, standard order is:

Налоговая база зависит от налогооблагаемого дохода.

This is the most natural order for a plain statement:

• subject
• verb
• prepositional phrase

Russian word order is flexible, so other orders are possible, for example for emphasis:

• От налогооблагаемого дохода зависит налоговая база.

This version puts more focus on what the tax base depends on.

So the original sentence is the most neutral and textbook-like version, but not the only possible one.

A useful breakdown is:

• Налоговая база = tax base
• зависит = depends
• от = on
• налогооблагаемого дохода = taxable income

Grammar structure:

• Налоговая база → nominative subject
• зависит → 3rd person singular verb
• от налогооблагаемого дохода → prepositional phrase with от + genitive

So the sentence pattern is:

[subject] + [зависит] + [от + genitive]

That pattern is very common in Russian.

Yes, stress is important in Russian pronunciation. The main stresses are:

• нало́говая
• ба́за
• зави́сит
• от
• налогооблага́емого
• дохо́да

A rough pronunciation guide:

• нало́говая ба́за зави́сит от налогооблага́емого дохо́да

For an English speaker, the long adjective налогооблагаемого can be the hardest part, so it helps to hear and repeat it in chunks:

• нало-го-обла-га́-е-мо-го

The biggest takeaway is this:

зависеть от + genitive = to depend on + noun

That means whenever you use зависеть, the thing after от usually goes into the genitive.

Examples:

• Это зависит от времени. = It depends on time.
• Цена зависит от спроса. = The price depends on demand.
• Результат зависит от подготовки. = The result depends on preparation.
• Налоговая база зависит от налогооблагаемого дохода.

If you remember just one grammar rule from this sentence, this is probably the most useful one.