You can easily update stock for product variants in Moon Invoice by following the steps below.

1. Open the Moon Invoice application on your device or tap on this link.
2. From the main menu on your left, go to Items ➜ Products.
3. Click on the three-dot icon (⋮) located in the middle-right corner and select Add Variations.
4. A dialog box will appear asking you to enter a Variant Type - enter your desired variant and click the Save button to apply the changes.
5. Once saved, the Update Stock option will become visible.
6. Scroll down to find the product variant you just added. Click on the three-dot icon (⋮) next to it to also access the Update Stock option.

Note: If you don't see the Update Stock option, make sure the Inventory checkbox (located under the Pricing & Tax section) is ticked. This will enable the stock update feature.