Answered by Shaykh Yusuf Weltch
After the husband has paid mahr to his wife, should they inform the elders or the witnesses during nikah that this obligation has been fulfilled to prevent the wife from lying later while divorce that mahr has not been paid? Is there a legal ruling requiring the couple to announce that mahr has been paid?
In the Name of Allah, the Most Merciful and Compassionate
No. There is no legal ruling that spouses must announce that the dowry has been paid nor for the payment to be witnessed.
However, the general encouragement to have any monetary transaction witnessed and written can also apply to the giving of the dowry. Quran chapter 2, verse 282, expresses the importance of committing debt contracts (the dowry is considered a debt once the marriage contract is in effect).
Allah knows best
[Shaykh] Yusuf Weltch