My company use multi currency. I want to use my own monthly rate. However, when I input the rate 1st working date every month, I found this rates will replaced?

Hello, chiu-billy-his-w.

I'll definitely help you out in entering your own monthly rate in QuickBooks Online. 

I take it that you're entering the rate on the transaction form itself (invoices, sales receipts, etc.). Entering your own exchange this way would always update the rate. 

So instead of entering the rate on the transaction form, let's go ahead and enter it on the Currencies page. Here are the complete steps: 

1. Go to the Gear icon menu, then select Currencies. 
2. Find your currency, then click the Edit currency exchange link. 
3. Select Your rate. 
4. Enter your custom rate.
5. Hit Save. 

We can now start using the custom rate for your transactions. 

If you need more help in managing your rates, I'll link these articles for you to use: 

• Learn about exchange rates in QuickBooks Online
• Enter and use your own exchange rates

I'll also add these articles if you need more help with the Multicurrency feature: About Multicurrency.

If you'd like to adjust your currencies for realized gains or lost in the future, this article can definitely help: Enter home currency adjustments for your foreign balances. 
 

Let me know if you have questions about managing your currencies and your related entries. I'm always here to help.