My hospital nurse advised that morning urine is best because hCG concentration is highest. If you test in the evening, make sure you haven't had too much water for a few hours before.
I tried testing in the evening once and got a very faint line that made me super anxious. Next morning it was a clear dark line, so I'd suggest waiting till morning if you can.
If you test in the evening, the hCG levels might be too diluted, leading to a faint or confusing line. If you are unsure, it's safer to get a beta-hCG blood test done through your doctor.