The forms of the gerund

The gerund is an -ing form. It can be simple or perfect, active or passive:

Note the changes in spelling when forming the simple gerund:

read » reading
study » studying
grow » growing
relax » relaxing
answer » answering
write » writing; argue » arguing (a final -e is omitted)
agree » agreeing (a final -ee does not change)
lie » lying (a final -ie changes to -y-)
put » putting; regret » regretting; readmit » readmitting (we double the final consonant if the verb ends in consonant-vowel-consonant, with the exception of w, x and y, and only has one syllable or has the stress on the last syllable)

In the negative, not usually comes before the gerund:

There is no point in applying for the grant.
There is no point in not applying for the grant.

In some cases, the verb in the main clause is negative, not the gerund:

I like getting up early.
I don't like getting up early.

As the gerund has no tense, it does not in itself indicate the time of the action that it refers to. However, it can show whether this time is the same as or earlier than the time of the verb in the main clause.

Simple gerund

The simple gerund can refer to the same time as that of the verb in the main clause:

I hate arguing with you. (arguing refers to the same time as hate: I hate when we argue.)
Tom suggested going back to our tents. (going refers to the same time as suggested: Tom suggested that we should go back to our tents.)

The simple gerund can also refer to a time before that of the verb in the main clause:

I don't remember saying anything like that. (saying refers to a time before don't remember: I don't remember that I said anything like that.)
She regretted not studying harder when she was at school. (not studying refers to a time before regretted: She regretted that she hadn't studied harder when he was at school.)

Perfect gerund

The perfect gerund refers to a time before that of the verb in the main clause. However, it is only used if the time of the action expressed by the gerund is not obvious from the context:

He denied being married. (the simple gerund being refers to the same time as denied: He denied that he was married.)

He denied having been married. (the perfect gerund having been refers to a time before denied: He denied that he had been married.)

If it is clear that an earlier time is meant, we use the simple gerund:

He denied stealing the car. (He denied that he had stolen the car.)

Passive gerunds

Passive forms are also possible:

I hate being lied to. (passive simple gerund: I hate it when people lie to me.)
He complained of having been unjustly accused. (passive perfect gerund: He complained that they had unjustly accused him.)