Thanks in advance
What it really means
Thanking you before you have agreed — polite on the surface, but it quietly assumes you will say yes. Some people find it friendly, others find it a little pushy.
Context, tips & common mistakes
"Thanks in advance" closes an email by pre-thanking for something not yet agreed — efficient for small routine requests ('please send the form — thanks in advance'), but subtly presumptuous for anything the reader might legitimately decline, because it books their compliance before they have offered it. Some British readers mind this more than others; enough mind it that the phrase is worth rationing.
Safer alternatives by situation: 'many thanks' (neutral, always fine), 'I'd be really grateful if you could…' (bigger asks), 'thanks for considering it' (requests that may be refused), 'no worries if not!' (favours between equals). Receiving 'thanks in advance' yourself carries no obligation — it is a style choice, not a contract — but it does tell you the sender considers the matter routine.
Example conversation
What you could say back
No spoken reply needed for this one.