when you say 100 submissions on the basic plan, is that per month, per year, or just 100 submissions total with no time period?

Please be noted that the submissions limit is per month. Accounts with Free subscription plan can receive up to 100 submissions per month/10 payments and store files up to 100MB. You may check the account status by clicking on User icon on the top-right corner while you are logged in to your account or from Usage section in your account settings.