Hi,regarding petty cash asset side showing Aed 971.but in expense it was 568.50/-there is difference 402.50.i cant find the proper amount.please help me

I'm here to ensure you're able to fix the difference in your petty cash account in QuickBooks Online (QBO), @asghar86-acca. 

You may haven't put cash into your petty cash account worth 402.50. That may be the reason there's a difference between the asset and expense sides. 

First, I'd suggest getting the deposit slip from your current account where you transferred money into the petty cash. This way, you'll be able to find the proper amount for it.

If you've verified that there's cash in transaction worth 402.50, let's create a cheque or bank transfer to record it. Just go to + New from the left menu. For more details, check out this article: Petty Cash Overview. Then, go to Put cash in under the How to manage petty cash section. 

If you've confirmed that there's no cash in, you can leave it for now. Once you use the petty cash yourself, that's the time to create an expense worth 402.50. That way, it will match the asset side, which is 971.

Lastly, I recommend going to the Account history of the petty cash account. It helps you keep track of all your transactions and the account's current balance. I'll guide you how. 

1. Go to Accounting from the left menu and choose Chart of Accounts.
2. Enter Petty Cash in the Search box. 
3. Locate the account. 
4. Click Account history from the Action column.

The screenshot below shows you the steps. For more information, visit this article: What Are Account Histories In QBO?. 

I'll be right here to help if you need further assistance. Enjoy the rest of your day, @asghar86-acca.