Working as designed.

When you post a RoG with no invoice, inventory value is increased with an equivalent posting to the Purchase Clearing GL account.  When you later post the RoI, that exact RoG amount has to be removed from the Purchases Clearing account... so when there is a mismatch between RoI and RoG, a variance is posted (so AP, PC and variance amount all together balance the posting). 

You can't retroactively correct the RoG cost during RoI... Sage 100 is not designed to allow it... and technically that inventory may already be gone (inventory amount translated into COGS).

There are a number of things to research here. Find out why they changed the unit cost when doing the ROG. Why was the cost on the purchase order changed prior to ROI.  You may have to do a Return of Goods, change the unit cost, do a receipt of goods with invoice. Now if you have sold some of the product you have an issue as it will create a variance you cannot correct. But the first thing is to investigate as to why the situation was created.

Thank you for your response. The inventory has not yet been sold. The individual who created the PO for some reason put in the wrong unit cost so when they did the ROG they didn't correct it. Then another individual went into the PO and changed the unit cost to the correct amount, but the ROG had already been completed which made it so the ROI and ROG did not match. So the ROI was not full processed, it was deleted. We followed your steps and did a return of goods and then we were able to change the unit cost. Thank you!

Thank you for your response. None of the inventory that was received had been sold yet thankfully. We ended up having to do a return of goods then go in and correct the unit cost, bring it back in and do a new ROG and then the ROI was completed.