If you want to use Inventory management on a new or an existing product/service, turn on the switch here

We make a new product named "My awesome service" for this tutorial

Then you can add Par level, Opening inventory, Purchase price

On the products page, you can see the current stock level

You can also see the stock level, under the Inventory value button

Here is our example product

If you want to increase the stock level of a product, you need to create a new expense

Select the partner from whom you purchased the product, or create an example partner just for that purpose

Select the product, you want to increase the stock, and add it to the Expense document by clicking it

When you are done, just click Save

As you can see the stock level of the product is raised from 100 to 120

If the purchase price is not 0, the amount of the expense document will appear in the business statistics

If you want to decrease the stock level of a product, you need to create a new Invoice