What should i do if my employee gets intimate with another employee in an office annual party?

What should i do if my employee gets intimate with another employee in an office annual party (corporate party) ? On the next day should i bring it to their notice that it's inappropriate or just ignore it ?

Dear Madhumita,
What type of party it was? Were there special invitees like valued customers or business partners? Was code of conduct circulated when the circular for the party was issued? Was it mentioned that this will be the "official" party? Where the party was conducted, was it in the company premises or somewhere outside?
One of the employees had been intimate with another employee. But then what was the reaction of the recipient employee? Did he/she accepted his/her advances or tried to spurn it? How are the relations between these two employees? Do they get intimate anyway?
I recommend you discuss the matter with the seniors. If the seniors give go-ahead then talk to the recipient employee and ask his/her reaction and try to probe what is in his/her mind? If the advances were against his/her wishes then tell him/her to submit the proper application. On the strength of the application, you can proceed further.
The recipient employee might want to lodge a protest but not in writing in that case call both the parties together and discuss this subject in front of them. Counsel to the recipient employee that discretion has to be exercised in all types of the official parties. Yes, parties do happen in an informal atmosphere. One may let one's down hair, nevertheless, crossing the line is dangerous and it could have negative repercussions on his/her career and additionally, such instances could vitiate the company environment.
Lastly, it is important for you to circulate a code of conduct before organising the party. Avoiding repetition of such instances is important.
Thanks,
Dinesh Divekar

It was a annual office party (Dance & hard drinks was also there)
Yes, clients from Japan were also present there.
Code of conduct for party- No
Party was conducted in a Restro lounge & bar
They been intimate with each other on mutual consent (smooching multiple times ).
Regards,
Madhumita Barua
HR - Recruiter/Operations
Pune

Dear Madhumita,
Since the two adults had physical intimacy with consent, we cannot do anything. Nevertheless, what happened was during the official party and not when they met in their personal capacity. As much romance in the office premises is prohibited the same rules apply even during office parties also. Therefore, you may call the couple and counsel. However, this has to be done by a person who is senior in rank to both the individuals who were involved in the physical acts of intimacy.
Maintain the record for the counselling and take the signature of both parties involved in the physical intimacy. I say so because today's intimacy could be tomorrow's case for sexual harassment.
However, taking a lesson from the episode, you need to create a "Policy on Workplace Romance". Though the policy could be for the workplace, it can be extended for the official parties as well. Whenever you issue a circular on the official party, you need to give reference to this policy for the code of conduct.
How the couple behaves at the workplace? Do they snuggle even at the workplace? They need to be told that their acts of intimacy are against the office culture and they must put a stop to it.
Thanks,
Dinesh Divekar