What is the latest time to pray Minchah?
Sundown.
If one forgot to pray before sundown and remembers a few minutes after, if it’s just a couple of minutes, Daven right then. If it’s already 10-15 minutes, you can Daven with a condition (Tnai). "If it’s still day, this is Mincha, and the next Tefilah is Maariv. If it’s already night, this is Maariv and the next Tefilah is Mincha (Tashlumin).
Thank you!