QuikStor Express does not currently support specials for an existing tenant. There are two ways to give a tenant a discount.
Give Free Rent
Giving free rent might be used in a scenario where, for example, tenants receive 1 month free when paying 6 months rent. This could also be used in the event a tenant needs to receive a percentage off the current months bill. This knowledgebase article covers how you would give free rent to an existing tenant:
Adjust Amount Due / Month
Another scenario is where an existing tenant qualifies for some type of discount each month on the unit. For a new move-in a special can easily be configured and applied at move-in. For an existing tenant, the amount due per month will need to be reduced manually by the discounted amount. This knowledge base article explains how to do that: