我把舊有發票(例如28/4/2020)重新輸入Quickbook系統, 但是庫存顯示是現有庫存(29/6/2020), 當我輸入發票資料,系統要求我要寫 29/6/2020 日期,否則不能執行指示,但此舉會令我現有庫存扣減了,我應該怎樣處理舊發票?

Welcome to the Community, @ayurbalahk-gmail. 

I used Google translator to help me understand your concern. To clarify, the prompt occurs when the invoice date is earlier than the As of date of the inventory item. 

To re-enter the old invoice without affecting the quantity on hand, you'll want to create another (non-inventory) item using a different name. Example: If the item name is Flower, you may use Flowers to make it something different. Then, ensure it's dated for April.

For future reference, check out these articles to help you learn more about how to make necessary changes to your inventory: 

• Change product and service item types in QuickBooks Online
• Adjust inventory quantity on hand in QuickBooks Online

Let me know if you have additional questions. I'll be looking forward to helping you more.