At the start of a sentence, we usually add a comma after introductory phrases, such as “on this occasion”, “on numerous occasions”, “on many occasions”, “on occasion”, “on a number of occasions”, “on the occasion of...”, etc.

At the start of a sentence, we usually add a comma after introductory phrases, such as “on this occasion”, “on numerous occasions”, “on many occasions”, “on occasion”, “on a number of occasions”, “on the occasion of...”, etc.

On this occasion, we would like to reiterate our concern regarding the volatility of financial markets.

The comma, however, is not strictly necessary if the introductory phrase starts with a preposition (like “on”), and the sentence is clear.

On many occasions the Commission has supported a range of projects in those regions.

But add a comma after long introductory phrases or signal that the adverbial phrase describes the whole sentence that follows.

On the occasion of the International Day of Education, we would like to reaffirm the role of education as an essential right that must be accessible to all people without any discrimination.

1. At the Beginning of a Sentence

When introducing a clear sentence with the adverbial phrases “on this occasion”, “on many occasions”, “on occasion”, “on a number of occasions”, “on numerous occasions”, “on the occasion of...”, etc. the comma is often optional.

On that occasion four organizations were accredited by the Institute of Technology.

On a number of occasions, the working group has met to discuss a number of important issues related to encryption policy.

The longer the introductory phrase, the more likely you will use a comma after it.

On the occasion of the 50th anniversary of the Universal Declaration of Human Rights, we should adopt action plans to reinforce the promotion and protection of freedom, justice, and peace in the world.

On occasion I do enjoy a glass of wine with friends while taking in the beauty of a sunset.

But always add a comma to clarify long or complicated sentences, even if the introductory phrase is short.

On that occasion, the European Parliament had not been considered this project because of a number of disputes regarding the use of nuclear energy.

2. In the Middle or at the End of a Sentence

Typically, we do not use a comma to separate the expressions “on this occasion”, “on a number of occasions”, “on many occasions”, etc. from the verb it describes.

The major said on numerous occasions that you should follow the guidelines on staying safe outside your home.

There are particular sentence structures, however, where commas may be necessary. For example, use a comma before but (or other coordinating conjunction, such as “and”, “or”, “nor”, etc.) to introduce an independent clause.

I have met Jennifer on several occasions, but I haven’t talked to her about her concerns for the county.