Optimal times for sending out invitations
Make an assessment of when would be best for your target group to receive the invitation. Regardless, it is recommended that you do not announce/invite before lunch on Mondays and/or after lunch on Fridays. On Mondays there is the risk of the email invitation to participate being drowned in a full inbox. On Friday afternoons lots of people are not at work and don’t read their email, so the invitation ends up waiting until Monday.
Avoid using deadlines
Using deadlines for surveys is not recommended. By using deadlines, you increase the risk of emails being put into a waiting list to be picked up again closer to the deadline, so other things are prioritized ahead of answering the survey. When the deadline approaches the recipient might have forgotten the survey. Rather write that you would like an answer as soon as possible.
Reminders as a new opportunity to answer
Use a friendly tone when writing reminders. Present the reminder as a new opportunity to answer and convey that the answer is still highly appreciated. Avoid using words like “reminder” in reminders, as this word can have negative associations for many people.
Survey reminders for interal vs. external relationships
For surveys directed at external parties, such as customers, one reminder is usually the maximum. More than that can be perceived as pushy, and can at worst damage the relationship.
For surveys conducted among internal parties, such as employee satisfaction surveys, you can send out two reminders. More than this will have minimal effect on the total response - if an individual has not answered after the first invitation and two reminders, the likelihood of the individual answering after a third reminder is very small.
Don’t wait too long to send out reminders
We know from experience that often more than half the responses come in on the same day the invitation is sent out. Thereafter, the percentage drops drastically for every day that passes. This means that reminders can be sent out soon after the main distribution, within 3 - 5 days preferably.