Based on the provided context, there is no explicit list of documents required to submit for a stamp duty valuation. However, the context does mention the process that occurs when an Assessor is of the opinion that an instrument liable to stamp duty has not been duly stamped. Here’s what can be inferred regarding the process:

1. Notice from Assessor: If an Assessor determines that an instrument has not been properly stamped, they will assess the value of the stamp duty payable and forward a Notice to the person liable to pay such duty.
2. Payment Time Frame: The Notice will specify the amount due and the time within which the payment must be made.
3. Procedure for Insufficiently Stamped Documents: The context implies that there is a procedure in place for when a document is insufficiently stamped, which would likely involve submitting the document in question to the Assessor.
4. Legal References: The provisions of Chapters XVIII to XXIV of the Inland Revenue Act relating to Assessment, Appeals, Determination of Appeals, and Finality of Assessments and the Recovery or Refund of Income Tax apply mutatis mutandis to the Assessment of stamp duty.

From this, one can conclude that the initial document required for a stamp duty valuation would be the instrument in question that is liable for stamp duty. Additionally, any Notice received from the Assessor would be part of the process. For a complete and accurate list of documents required, it would be advisable to consult the relevant sections of the Inland Revenue Act mentioned or seek guidance from a licensed attorney or the office of the Assessor.