Overview

Amazon sellers frequently encounter Error 13009 when bulk‑uploading inventory files that contain sale start dates in an unsupported format. The validation failure stops the file from processing, delaying time‑sensitive promotions such as Lightning Deals or seasonal discounts. Correcting the date format restores the upload and ensures pricing changes go live as scheduled.

Key Points

• Root cause — The error appears when the sale start date field does not match Amazon’s required pattern, causing the entire file to be rejected.
• Exact format — Amazon mandates a four‑digit year, two‑digit month, and two‑digit day separated by hyphens (e.g., 2024‑11‑15).
• Logical ordering — The start date must precede the sale end date; a start date that is the same as or later than the end date triggers the same error.
• Spreadsheet auto‑formatting — Programs like Microsoft Excel automatically convert entered dates to regional formats (e.g., 11/15/2024), which silently breaks Amazon’s validation rules.
• Bulk impact — When a column is auto‑formatted, dozens or hundreds of rows can inherit the wrong pattern, leading to large‑scale upload failures.

How the Error Occurs

1. File submission — You upload a completed inventory template through Seller Central. Amazon’s backend scans each column for required data types.
2. Date validation — The system checks the “sale_start_date” field for the YYYY‑MM‑DD pattern and verifies that the date is earlier than the corresponding “sale_end_date”.
3. Rejection — If any row fails either check, Amazon returns Error 13009 and halts processing of the entire file.

Example: A seller enters “12/01/2024” for a flash‑sale start date. The spreadsheet converts it to “12/01/2024”, but Amazon expects “2024‑12‑01”. The mismatch triggers the error, and the file is rejected.

Preventing Spreadsheet Auto‑Formatting

• Set column to Text before entry — In Excel, select the entire “sale_start_date” column, open the Format Cells dialog, choose “Text”, and then type dates in the required format. This forces the program to treat the input as plain characters rather than a date value.