What Happens to the Holding Deposit 15 Days After it Was Paid, if no Tenancy has begun?

The system doesn’t automatically alert you 15 days after taking a holding deposit. 

If needed, you can create a mandatory tenancy UDF requiring a deadline date before a tenancy can be saved.

The workflow would be:
 

1 - Applicant pays the holding deposit.

2 - To record it, attach the applicant to a prebooked tenancy.

3 - Create the prebooked tenancy with a UDF deadline date (e.g., two weeks ahead).

4 - Bring the funds in under that prebooked tenant.

5 - On the Lettings Activity list, a header like “UDF Holding Deposit Deadline” will show all prebooked tenancies approaching their deadline.

Further Reading: Refunding Tenant Holding Payments in CRM