::Question are you trying to correct it from the mobile device if so this is a great article Why you can’t reverse a purchase registration in WHS in AX 2012 R3 | timsaxblog (wordpress.com)
If are in AX mind you its been a while and I do not have a test system any more it an end life system
This might be able to help
Step 1: Create a Correction Journal
To fix an incorrect quantity received against a purchase order, the first thing you need to do is create a correction journal. Go to Inventory Management > Journals > Item Counting > Correction. In the correction journal form, you will need to select the warehouse where the goods were received, the purchase order number, and the item in question. Next, fill in the details of the correction; in this case, the correct quantity received.
Step 2: Post the Correction Journal
After creating the correction journal, the next step is to post it to the system. To do this, click on the Post button located on the toolbar at the top of the correction journal form. Once the journal has been posted, the quantity in the warehouse for the item will be updated, reflecting the correct amount received. However, the purchase order will still show an incorrect quantity.
Step 3: Create a Purchase Order Correction
To update the incorrect quantity on the purchase order, you will need to create a purchase order correction. Go to Procurement and Sourcing > Purchase Orders > All Purchase Orders. In the all purchase orders form, locate the purchase order in question and click on Edit. In the Purchase order form, go to the Corrections tab, and create a new purchase order correction. In the correction, fill in the details of the adjustment; in this case, the difference between the incorrect quantity received and the correct quantity.
Step 4: Approve the Purchase Order Correction
Once the purchase order correction has been created, it will need to be approved. To do this, go to the Purchase order correction form and click on the Submit button located on the toolbar at the top. After submission, the correction will be sent to the appropriate person for approval. Once approved, the purchase order will be updated, reflecting the correct quantity received.
Step 5: Mark the Correction as Complete
After the correct quantity has been updated on the purchase order, the last step is to mark the correction as complete. Doing this ensures that the correction will not be processed again and that the incorrect quantity will not be mentioned on any reports. To mark the correction as complete, go to Inventory Management > Journals > Item Counting > Correction. Locate the correction journal in question and click on the Complete button located on the toolbar at the top of the form.