For the free plan, does the 100 form submission reset every month?

Hi @namooch, yes it does. You will get your submissions replenished on the first day of each month. 

Keep in mind though that the 100 Monthly Submissions limit is different from the 500 Total Submission Storage limit.

100 submissions is per month - Gets replenished on the 1st day of each month

500 total submission storage - Doesn't get replenished and is the hard cap for the free plan

To get further submissions, you can either delete existing submissions to make room for more or upgrade.

Hope that answered your question.