Arigato: Arigatou Gozaimasu vs. Arigatou Gozaimashita
Arigato (also spelled Arigatou) is one of the best-known Japanese words, meaning thank you. It is an expression of gratitude often used towards friends or those younger than you.
If you want to say Arigato (pronunciation) to people like bosses, superiors, seniors, or strangers, you should use Arigatou Gozaimasu or Arigatou Gozaimashita.
Arigato vs. Arigato Gozaimasu vs. Arigato Gozaimashita
Arigato Gozaimasu and Arigato Gozaimashita are polite ways to say Arigatou, and both translate to thank you very much. But these phrases are slightly different in usage.
Arigato Gozaimasu (ありがとうございます)
Arigato Gozaimasu (pronunciation) is a present tense used right after something you’ll appreciate has been done. For example,
if you get a no-charge extra service when dining in a restaurant, Arigatou Gozaimasu is the best answer among these three phrases.
Arigato Gozaimashita (ありがとうございました)
Arigato Gozaimashita (pronunciation) is the perfect tense of Arigato Gozaimasu. This phrase is used when or after the event involving what you are thanking for has ended. For example,
in the continuation from the above case, when you finish dinner and leave the restaurant, you say Arigatou Gozaimashita, not Arigatou Gozaimasu here.
By the way, Arigato (pronunciation) can be both the present tense and the perfect tense. For example, when you are gifted something from your friend, you say Arigato here.
And next time you meet that friend, you can say 先日はありがとう, meaning thank you for the other day.