SendGather sends each person their own link, shows you who still owes you something, and chases them until everyone is in. For businesses collecting from clients and vendors, and non-profits collecting from volunteers and constituents. No subscriptions. No accounts for the people you ask.
Chasing folks down for stuff is a pain, emails fall through the cracks, and standard web forms don't chase people for you. I'm sure there are enterprise tools that do this, but I couldn't find anything that serves smaller orgs and non-profits. I also don't like recurring subscriptions, so this is strictly pay-per-ask.