I've got you covered, @anjum.

You can use the multicurrency feature in QuickBooks Online (QBO) to reflect the currency to an invoice in SGD. Here's how to set it up:

1. In your QBO account, select the Gear icon and choose Account and Settings.
2. Click the Advanced menu.
3. Choose the Currency section and click your Home Currency.
4. Turn on the Multicurrency checkbox, then confirm.
5. Click Save, then Done.
   
   

Once done, you can now add the currencies you use. Let me walk you through:

1. Choose the Gear icon, then click Currencies.
2. Select Add currency.
3. From the Add Currency drop-down, choose the new currency.
4. Click Add.
   
   

Then, you can already use the currency when creating the invoice in your QuickBooks Online account. 

I'm also attaching this resource for additional information: Turn on and use multicurrency.

Additionally, you may check out these articles to learn more about this feature:

• Multi-currency FAQ.
• Learn about exchange rates in QuickBooks Online.

Feel free to comment below if you have other questions about managing your invoices in QuickBooks. I'll be around to help you. Keep safe!