1. Generally, the three most common validation errors you will see on the EDGAR site are incorrect schema in the XML build (columns in the wrong order, or unexpected outputs in a column, etc.) the CUSIP not formatted correctly or non-round market values present.Schema – Unfortunately, you will have to create the schema again using Excel. The instructions are here: https://www.sec.gov/info/edgar/quick-reference/13f-xml-information-table.pdf
2. In terms of CUSIP issues, it is recommended NEVER to open your raw files in Excel unless you are able to make the CUSIP column text formatted before it is imported. A text column will maintain the leading zeros and not turn a CUSIP into a scientific number. Depending on the version and settings in Excel, you may not be able to change the formatting to text once opened and scientific numbers will never be able to be reversed.
3. For non-round market values, you will have to adjust the raw data in Excel by either using a formula or cell format changes (depending on your version of Excel).