Correct spelling, explanation: transferred is a past participle form of a verb transfer. This form is created according to the rule that says if the verb ends with a vowel and a consonant, and the accent is on the last syllable, the last consonant should be doubled before the suffix -ed. Therefore, the correct version is transferred and not transfered.

Definition of transferred:
verb: past participle from transfer
– to transform, change or move from one place, situation, person, group, job, etc. to another;
When we discovered that millions were illegally transferred from our company accounts by a group of employees, our internal investigation had to be transferred to the police hands.
– to legally make something a possession of someone else;
Betty wanted to have all her possessions transferred to the charity.
– to arrange for someone that the received phone call can be answered on another device;
Have you transferred my phone calls to John while I was out of the office?

Incorrect spelling, explanation: transfered is the misspelled version of the past participle from transfer. Transferred is created by adding suffix ed to a verb transfer, however, it is a verb that ends with a vowel and a consonant and the accent is on the last syllable, so the consonant r has to be doubled. This is why the version transfered is not correct, because the doubled consonant is missing there.