Afrikaans verbs usually do not change form according to the subject in the present tense.
So you get:
That is why the sentence uses verander, not a special form meaning changes.
Here verander means change in a transitive sense: to change something or to alter something.
In this sentence:
But verander can also be used intransitively:
So the verb can work both ways depending on the sentence.
Because netto is one of the adjectives that usually stays unchanged before a noun.
Many Afrikaans adjectives take an -e ending when placed before a noun, but some borrowed or fixed-form adjectives do not. Netto is one of those.
So:
This is similar to other words such as:
A simple English-friendly approximation is too-lie.
A slightly more careful breakdown:
So toelae is approximately too-lie.
Afrikaans normally uses double negation.
So the negative sentence is:
Die toelae verander nie die netto salaris nie.
Notice the two nie words:
That double nie is a very important Afrikaans pattern.
A very common past-tense form in Afrikaans is the het + past participle structure:
Die toelae het die netto salaris verander.
This can mean:
Afrikaans often uses this perfect form where English might use either simple past or present perfect.