A single-select standard lookup to assign the Transaction Status. This defaults to "New" but can be changed to "Approved" or "Ready to Post". This defaults to 'New' and is always required. This field is editable until the transaction is 'Ready to Post'. Updating the Status does the following:

New: This is the default value. While in the Status of New all editable fields are open for edit, no posting/approval validations are performed, GL Dates are not assigned, and journal entries are not created. If the transaction was moved back from Approved to New, the GL Date will be assigned and a Journal Entry will exist.
Approved: Performs all the data validations required to post the transaction. If one or more validations fail, messages are provided indicating what needs to be corrected. If all the validations pass, then all the fields are disabled except for the Status lookup (and any fields that are always editable), journal entries are created/updated, journal ID's are assigned to the journal entry, and blank 'GL Dates' are assigned.
Ready to Post: Runs the Approval validations. If one or more validations fail, messages are provided indicating what needs to be corrected. If all the validations pass, then all the fields are disabled with the exception any fields that are always editable and updates the Transaction Status to "Posted".