French phrase
Je vous remercie par avance de ~.
Meaning
Thank you in advance for ___.
When to use it
A polite expression of thanks given before help is provided. It is common in requests and does not imply a promise.
Example dialogue
Je vous remercie par avance de votre aide.
Thank you in advance for your help.
Pas de problème, je m'en occupe.
No problem, I'll take care of it.