If you posted wrong document date or posting date, you might want to change it for the period of report purpose.
If you are an administrator, you may change it with your authority in object designer.
First step, please make sure what is the correct date.
Then revise accordingly in below table:
1. Purchase invoice header
2. Purchase invoice line
3. G/L Entry, if you are posting under inventory category, please search for the direct cost as it will impact on inventory costing.
4. Vendor ledger entry
5. Value entry
6. Item Ledger entry
After all have been revised, kindly cross check in vendor card, ledger, item, posted purchase invoice.
It may caused by customer group code in customer card.
Go to customer card, customer dimension and choose the customer group code that you needed.
It shall ever to post then.
The following steps are not foolproof yet but it has helped me solved many average cost issues.
1) At item card, click on Item --> Entries --> Value Entries to open the value entries screen.
2) Copy all records in the value entries screen to Excel.
3) In the Excel sheet, sort the records by Valuation Date.
4) Add a column called Cost Amount to the Excel sheet. Cost Amount = Cost Amount (Expected) + Cost Amount (Actual). Use Excel formula to populate the Cost Amount column for all records.
5) Add a column called Cost Amount (Accumulated). As indicated by the column name, it is the accumulated value of Cost Amount from first record to the last record. Again use Excel formula to populate this column.
6) Add a column called Quantity (Accumulated). Quantity (Accumulated) is the accumulated quantity from first record to the last record. Use Excel formula to populate this column.
7) Add a column called Avg. Cost. Avg. Cost = Cost Amount (Accumulated) / Quantity (Accumulated).
8) Now, look for the last inbound entry record for each Valuation Date. The Avg. Cost for the last inbound record for each valuation date is the average cost for the day.