The Stock inventory system you choose is extremely important and it can not be changed once saved, so consider which configuration you want carefully.
Go to Settings > Stock Control > Stock inventory system
- First in first out: This means that the first stock items entered will be the first items taken out.
- Last in first out: This means that the last stock items entered will be the first items taken out.
This setting is required to be set before you can proceed with the Stock Feature.