T90D

T90D provides the broadest and most stable of Amazon’s standard rolling time windows (T30D, T60D, T90D).
Because it spans roughly a quarter, it allows Amazon, vendors, and sellers to:

• observe sustained performance patterns
• remove noise from short promotions or temporary stockouts
• identify early seasonal changes
• validate long range forecasts and replenishment plans

T90D is especially useful for categories with slower sales cycles, high price items, or seasonal fluctuations.

Where T90D is used:

• Vendor scorecards and WBR or QBR reviews
• Long term advertising performance analysis
• Retail profitability studies
• Inventory health metrics (STR, OOS, Buyable percent)
• Quarterly forecasting inputs
• Category or brand level performance snapshots

Why T90D is important:

• Provides a realistic quarterly trend
• Reduces the impact of single events: Lightning Deals, Prime Day, short OOS periods
• Helps identify whether sales lifts or declines are structural or temporary
• Supports planning for major retail cycles like back to school or Q4

Example:
If today is October 1, the T90D period spans July 3 through October 1.
A vendor reviews T90D shipped revenue and notices a consistent downward trend across all 90 days, indicating true demand softening rather than a temporary dip.

Benefits for Sellers and Vendors:

• Stronger insight into real demand shape
• More reliable reorder planning
• Clearer understanding of advertising or pricing impact over time
• Visibility into seasonality and category shifts

Benefits for Amazon:

• Better supply chain and FC space allocation
• Accurate category trend modeling
• Improved long term forecasting and PO planning

In short:
T90D (Trailing 90 Days) is the rolling 90 day period Amazon uses to measure long term performance trends across sales, traffic, ads, and inventory health.