Can I drop off a rental after hours?

Yes, they have a key Dropbox

Yes

The Scotch Plains location allows after hours drop off. The Greenbrook and South Plainfield locations don't.

I had to do that a few years ago & it was no problem. I can't imagine why it still wouldn't be true. I seem to remember the Enterprise website having live chat help. (They'd confirn.) Drop off after hours MIGHT roll you into an additional day rental & (for example) since Scotch Plains isn't open Sunday, that might roll into Monday 7am drop off on your rental days. The rental agents at Scotch Plains (& Green Brook for that matter) have always been real good to me about not getting picky on refilling gas, being technically late 2 hours for drop off (my example: 50 hrs from pickup to drop off was 'forgiven' and still just a 2 day rental). Also: If you need a pickup or drop off to/from home/work or an auto repair shop, they now (often) arrange and pay for Uber so, if you used Uber or Lyft & showed them the e-receipt Monday, I wouldn't be surprised if (dropping off now), that would be ok 'proof' to wave paying for Sunday. Check Green Brook to. They may be open.

Yes, there is a box by the door to drop the rental keys in.