Reconciling Wildberries financial reports: Why totals match but item-level data fails

The author analyzes the issue of financial data discrepancies when working with the Wildberries marketplace. Although total account balances match the platform's reports to the penny, detailed profit calculations per SKU are often incorrect. The article explains why matching top-level figures does not guarantee data accuracy at the individual product level. It details a reconciliation methodology using two independent data sources to identify calculation errors. Common technical pitfalls are discussed, such as incorrect column mapping, sign errors in operations, and file processing issues. This article is useful for developers and analysts working with marketplace API integrations, as it offers approaches for creating reliable invariants to ensure data quality and automate financial reporting.