Correct spelling, explanation: this word is a combination of a verb attend, which means simply to take part in something (an event) and a suffix -ance, which is normally used to create a noun from a verb- it can also be explained as astate of. There is no reason to replace a with an e, therefore the form attendence is incorrect.

Definition of attendance:
1. noun, the fact that someone is present somewhere (at an event, meeting, party, or school)
He really put attention to his student’s attendance.
What do you mean you are not coming? This is the most important event of the season, attendance is nearly compulsory!
2. noun, number of people taking part in something (meeting, event)
Sorry, you’re not on the attendance list so I can’t let you in.
I guess the first time in our band’s history we had such attendance at a concert.

Idioms and phrases with attendance:
→ to dance attendance on, to do everything in your power to please somebody or to make their life as easy as possible: Your child is so spoiled! It looks like someone has to dance attendance on her all the time.
→ to be in attendance, to take part in some important, often very official event: The Prime Minister was in attendance at the funeral.
→ to take attendance, to check, for example at the beginning of the classes at school, if all students from the list are present: This is very important to take attendance on the bus before we leave for our trip.

Incorrect spelling, explanation: as the main form comes from a verb attend (to participate, take part in, or be present somewhere) and a suffix -ance: attend + ance=attendance, it is mistaken to write attendence.

Incorrect spelling

Incorrect spelling