If for any reason the service will be terminated within the period of validity, a relevant explanation must be included on the savings certificate. Please specify the conditions, such as "For the first __ people only", "Valid between the dates __ and __", "Valid on weekdays only", etc.
Changes or cancellations to service made after the publication of the magazine can be subject to customer claims. In circumstances beyond your control, please be sure to make such changes or cancellations with the understanding of your customers.

Since savings certificates are generally clipped out and used, please collect them from customers when they are used in exchange for the promotional service you provide.
If you have chosen "Valid one time only", this means that the certificates "Cannot be copied"; in other words only certificates clipped out directly from the pages of the magazine will be valid.
"Can be used multiple times" means that it is "OK to make copies" of the certificates. In this case, even certificates clipped out from a photocopy of the magazine will be valid for use.

It will be best to write a description of the promotional service you provide clearly and in a manner that anyone will be able to understand without confusion.
The savings certificate is something you will get the most out of as a sales promotion tool. Try to make yours as straightforward as possible, and avoid complicated stipulations. They are best used to provide promotional incentives to shoppers that make them think "I got a good deal :-)", even on a modest scale, while encouraging their selection of your product or service.