You're very lucky if you can get your chairpeople to actually complete a post-event form. It's been my experience that by the time the event is over, they've had it and want to just close the binder and file it away! Horrible for future planning
Anyway, the best way to get a response is to make the form as easy to complete as possible - check boxes rather than essays, for example, and short specific questions. Here are some ideas:
The best idea we had:
The biggest problem we faced:
We had way too much:
We ran out of:
If we do it again, we should:
Approximate number of volunteers we needed:
Approximate number of people who participated:
The date we started planning:
How much we spent:
I would expect any computer-generated documents or flyers to be copied to disk and kept with the project files.
Also, the treasurer should send a summary report of all the financial transactions that the treasurer handled back to the chairperson for filing in the event files. Ideally, the treasurer should also copy the detailed receipts that were sent in for reimbursement and give the copies to the chairperson. It can be extrememly helpful to go back and look at how many popsicles were purchased, for example. At minimum, those receipts should be kept in the treasurer's files even if no backup copies are made.
If you print the form on colored paper and set a deadline for returning it to the Exec Board, you will increase your chances that the report is done. Keep a copy in the Exec Board (VP's?) files and send the original back to the chairperson for filing. The more places the info is kept, the more likely it can be found next year.