“Thanks”, “thank you” are two basic way to express your gratitude. “Thanks” is more informal than “thank you”.
1. Thanks a lot.
2. Thanks very much.
3. Thank you very much.
4. Thank you so much.
If you want to express you are thankful in a extremely polite way, you can say as listed above.
Thank you so much for helping me out today.
“You’re looking well.” “Thanks.”
Thank you very much for dinner – it was great.
Thanks a lot for looking after the children.
Thanks very much for making dinner tonight.
5. Thanks a bunch
Sometimes informal way to say someone does a disservice.
You told Tony what I told you in confidence? Thanks a bunch!
Thanks a lot for spoiling my lovely evening.
6. Much obliged
This is the most formal way to say thanks, and it is now rare used.
“I am much obliged to your ladyship for your kind invitation, ” replied Elizabeth, “but it is not in my power to accept it.”
7. You’ve saved my life
8. I owe you one/I owe you big time.
Thanks for giving me a lift to the station. You saved my life.
Thanks for the advice. I owe you one.
Thanks for helping me out with the essay. I owe you big time.
9. You shouldn’t (have)
When you receive others’ gift with surprise, you can say so.
Oh, Martin, what lovely flowers. You shouldn’t have!
10. You’re too kind
Thank you for for the glowing praise. You’re too kind.
Peter stood by me when I most needed it. I’ll always appreciate that.