Can one entity with a common GST No act as customer and supplier to us. I've this case we buy services and supply products to this entity

I'm here to help you set up profiles in QuickBooks Online (QBO), @contact150.

Allow me to discuss some details on how you can do this.

In QBO, you can set this entity as a supplier and customer. Just make sure to add special characters since the program doesn't allow creating profiles with the same name. Also, when setting them up, you can choose the appropriate GST registration type for them to ensure they are correctly classified. Please refer to the steps below.

Set up supplier:

1. Go to the Expenses menu and choose Suppliers.
2. Next, click the New supplier button.
3. Enter the name and add an indication that this is the supplier profile of the entity.
4. Then, under the GST registration type field, pick the correct type.
5. Complete the details of the remaining fields. 
6. When done, select Save.

Create a customer:

1. Navigate to the Sales menu and select Customers.
2. Then, click the New customer option.
3. Type the name and add a special character to indicate that this is the customer profile of the entity.
4. Next, choose the correct type under the GST registration type field.
5. Complete the details of the remaining fields. 
6. Once finished, click Save.

I've also added this article to guide you in tracking the product and services you buy and sell: Add product and service items to QuickBooks Online.

Just in case you'll need to check the status of your inventory as well as the ones you buy or sell, you can run inventory reports in QBO. 

I'm always ready to lend a hand if you have any other concerns about managing your customer or suppliers profiles. Feel free to leave a reply below. Have a good one.