Question: Can the mark as paid date be changed once it is entered?
Answer: Version 1 does not have a facility to change the mark as paid date once it has been submitted. This functionallity will be added to Version 2.
WorkAround: First, re-enter the existing record information on a new Input Record form, and then remove the old, incorrect record using the Delete Record action. Once you have done that, the Mark as Paid field will be ready for your correct paid date. When you delete the old, incorrect entry, ensure that you delete the right record because that action cannot be undone.