What is Materiality
If something is material then it means something and has an impact. If something is immaterial then it is said to be insignificant. This term is used in the accounting and legal arena.
If a multi million pound company forgot to include in its accounts a receipt for £5 then it would not be seem as making the final accounts not a true and fair statement. It can just include it in the next year. It does not matter.
If a person who is accused of stealing has been seen on camera somewhere else at the time the crime was committed then it would be material to the case.