If one is up til halachic midnight, does one have to go to sleep to say tikun chatzos or can one recite it anyway.
It's hard to prove a negative. But I just reviewed the halachot of Tikkun Chatzot in Yalkut Yosef 1:17-34 and there is not even mention of sleeping beforehand, although indirectly it does say in 1:17 that "every devout Jew should rise...", which at most sounds like an assumption that people are likely to be asleep at midnight, not that they must be asleep in order to fulfil the mitzva of Tikkun Chatzot. In fact, 27 says:
"If someone realizes that if he says tikkun chatzot before sleeping (קודם שילך לישון), he will not be able to get up in the morning in time to pray shacharit at netz, it is still better to recite tikkun chatzot..."
So I don't think there is any issue. But please ask your rabbi.