Which statement regarding an appraiser's workfile is correct?

The assertion that the workfile must exist before the report issuance is correct because appraisers are required to maintain a comprehensive workfile that supports their valuation conclusions. This workfile serves as evidence of the data, analysis, and rationale that went into the appraisal process, ensuring that the appraisal can be substantiated if challenged. The existence of a workfile prior to the issuance of the report is also a critical aspect of maintaining transparency and accountability in the appraisal profession.

In addition, the requirement for the workfile to be in place before the report is issued aligns with established standards in the appraisal industry, which emphasize the importance of documenting the appraisal process. Such practices help ensure that the appraiser's conclusions are well-supported and defendable, reflecting the diligence and thoroughness expected of a professional appraiser.

The other options do not align with standard practices or regulatory requirements: destroying the file after a specific period is not typical, the annual review of the workfile is not mandated, and while digital copies can be included, the workfile is not limited to just digital formats, allowing for flexibility in documentation methods.