Sir I am an Accountant and offering accounting services. Can I use this quickbook account to different small business to prepare their accounts.

I appreciate your interest in using QuickBooks Online (QBO) for your accounting services, ali. You made a great decision choosing us.

It is indeed possible to manage the bookkeeping of multiple small businesses using a single QBO account. To access your client's books, you can make use of a QBO Accountant account. Your clients will need to invite you as their accountant in their company file or ask them to invite you. Here's how:

1. Ask your client to send the invite to the active email address you are using in QBO.
2. Open the email and click the Accept Invitation link.
3. Sign in with your user ID and password.

After doing so, you can now open and review their books. 

For further information, check out this article: Add clients to QuickBooks Online Accountant.

I can help you out if you need further assistance managing your client's files. Just drop your query below, and I'll get back to you.