You committed the budget in March. You find out in September.
You commit open-to-buy in March against a spreadsheet and a feeling. Your supplier's forecast is a sales target wearing a forecast's clothes. You negotiate hard on margin in January and hand it all back in markdown in September, and everybody calls that the cost of doing business. Your supplier brings an analyst to that meeting. What do you bring?
What changes on Tuesday.
A forecast that thinks: seasonality, trend, paydays, promotions, and a lead time for every product and supplier rather than one number for the lot. Cannibalization modeled before you commit, not discovered in the post-mortem. A lifecycle profile, so you know the shape of the curve before you buy the top of it.
The proof: Every order shows the lead time it was sized to and where that number came from: the product, the supplier or your default. Measuring what each supplier actually delivers against what they promise is in build.
For you: You walk into the supplier meeting knowing the lead time every order was sized to, and what it would take to move the inventory you are both looking at.