Hi @LouiseDepaquis, I'm afraid I don't know how far you are through Level 2, so I hope the below reflects what's in your model. I agree that the issue arises from the reference to 'Beginning Inventory' (a good way to identify the problematic part of a formula is to try out each part of the formula individually i.e. if you just make the formula for 'Suggested Order Amount for the Month' equal to 'Beginning Inventory', you will get the same circularity error). The likely reason that 'Beginning Inventory' is causing issues is that it contains PREVIOUS(Ending Inventory) and 'Ending Inventory' references 'Confirm Purchase Order Receipt'. 'Confirm Purchase Order Receipt' is the problem, as the formula contains POST(Final Shipment Amount, Final Shipping Time Weeks). The POST function can actually take a negative number as its second argument (the number of periods to offset the value in the first argument), which means it then posts the value into the past instead of the future. So if 'Final Shipping Time Weeks' is negative, the function posts the value for 'Final Shipment Amount' into the past. This is a problem as the formula for 'Final Shipment Amount' references 'Suggested Order Amount for the Month' so, if somehow the 'Final Shipping Time Weeks' is a negative number (in this example -1), the formula references result in the below circular reference: As I mentioned above, the formula for 'Confirm Purchase Order Receipt' contains POST(Final Shipment Amount, Final Shipping Time Weeks). Naturally, in practice it's impossible to have a negative shipping time however, as the second argument refers to a line item (which could return a negative value), the calculation engine cannot exclude the possibility that the second argument in POST might be negative and thus result in circularity, so it throws the circularity error that you have seen. (In this particular example, the circularity does not occur when a positive value is used as the offset instead of 'Final Shipping Time Weeks' in the formula for 'Confirm Purchase Order Receipt', e.g. if the formula contains POST(Final Shipment Amount, 2) instead, 'Suggested Order Amount for the Month' can reference 'Beginning Inventory' without any circularity occurring.) This is my understanding of it, but if anyone spots any mistakes please jump in and correct me! Hope this helps 🙂 Best, John
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