Arigato Gozaimasu vs Sumimasen: Which Should be Used?
“Arigato (ありがとう)”, also spelled Arigatou, meaning “Thank you”, is a basic Japanese phrase that many people know. And the polite form for the word is Arigato Gozaimasu.
Meanwhile, as I wrote in this article, Sumimasen (Suimasen) basically means “I’m sorry” and is used when the speaker is feeling anxious or guilty about something.
Arigato Gozaimasu vs. Sumimasen
But when someone has done a kind thing for you, many Japanese people tend to use Sumimasen instead of Arigato Gozaimasu.
For example, when a stranger holds a door open for one, the person might say “Sumimasen”, just expressing a thank you without a sense of guilt.
If the person says “Arigato Gozaimasu” here, the one holding the door open will most likely be glad.
But using “Sumimasen” for showing gratitude here can be interpreted in various ways, and the hearer might think negatively, like “I made the person feel sorry.”
So as some people recommend, it would be better to use “Arigato Gozaimasu” when others do kind things for you.
(Reference Page: Benesse.jp )