買樓,在成交後,前業主透過律師行發信件追討多交了的一個月管理費用。?

所以前業主是代墊管理費用嗎?發信是什麼信件?
您的說法比較抽象, 陳述未必完整精確, 建議提供較具體的事實供判斷

1. No. The previous owner is correct, as you have been beneficial from the extra payment.

2. The worst case is you will be sued for the fee in the Small Claims Tribunal. However, the lawyer conducting this transaction will be in a way bigger trouble.

My suggestion is check with the transaction document as well as the property management. If what the previous owner said is true, simply either ask the management to refund it or you pay it back.