Tekjuskatturinn er hár.

In Icelandic, the definite article is usually added to the end of the noun instead of written as a separate word.

So:

• tekjuskattur = income tax
• tekjuskatturinn = the income tax

In this noun pattern, the definite nominative singular form ends in -urinn, so skattur becomes skatturinn. The same thing happens inside the compound tekjuskatturinn.

The base form is tekjuskattur.

This is a compound noun:

• tekju- = a combining form related to income/revenue
• skattur = tax

Then the definite ending is added:

• tekjuskattur → tekjuskatturinn

So the whole word is basically income-tax-the.

It is:

• nominative
• singular
• masculine

Why?

• It is the subject of the sentence, so it appears in the nominative
• It refers to one tax, so it is singular
• The noun tekjuskattur is a masculine noun

This matters because the adjective has to match it.

Because Icelandic adjectives agree with the noun they describe in:

• gender
• number
• case

Here, the subject is masculine singular nominative, so the adjective appears as hár.

Very roughly:

• masculine: hár
• feminine: há
• neuter: hátt

So hár is the form that matches tekjuskatturinn.

Because hátt is the neuter form, while tekjuskatturinn is masculine.

A learner may also confuse hátt with the adverb form in other contexts, but here high is an adjective describing the noun income tax, so it must agree with that noun:

• tekjuskatturinn er hár = the income tax is high

If the subject were a neuter noun, then hátt could be correct.

Yes, hár can mean both tall and high, depending on context.

For example:

• with a person: tall
• with a tax, price, number, wall, or mountain: often high

So in Tekjuskatturinn er hár, the natural meaning is high, not tall.

Because this sentence is a full clause, not just a noun phrase.

Here the structure is:

• Tekjuskatturinn = subject
• er = is
• hár = predicate adjective

So the sentence means The income tax is high.

That is different from a noun phrase like high income tax. If you wanted to say a high income tax, the adjective would normally come before the noun:

• hár tekjuskattur

So the position changes because the grammar is different.

Er is the present tense, third-person singular form of vera, which means to be.

So:

• er = is

It links the subject to the description:

• Tekjuskatturinn = the income tax
• er = is
• hár = high

Yes, but the nuance changes.

• Tekjuskatturinn er hár = The income tax is high
• Tekjuskattur er hár = more like Income tax is high or an income tax is high, depending on context

With -urinn, the noun is definite and specific. Without it, the statement is more general or less anchored to a specific known referent.

Yes. This is a very normal Icelandic main-clause pattern.

The order here is:

• subject
• finite verb
• complement

So:

• Tekjuskatturinn
  • er
    • hár

Icelandic is often described as a verb-second language in main clauses. In a simple sentence like this, that gives the very natural order you see here.

A rough learner-friendly approximation is:

• Tekjuskatturinn ≈ TEK-yu-skat-tu-rinn
• er ≈ ehr
• hár ≈ howr

A few useful points:

• Icelandic words are usually stressed on the first syllable
• á is a separate letter, not just an accented a
• á is pronounced roughly like ow in now

So hár does not sound like English har.

The accent mark is important in Icelandic. It is not just optional spelling decoration.

In hár, the á is a different vowel from plain a. It changes the pronunciation and helps distinguish words and forms.

So when reading Icelandic, you should treat letters like á, í, ó, ú, ý, é as real separate letters with their own sounds, not just stressed versions of ordinary vowels.