You may receive this error when trying to book stock manually from the system:
The main cause for this is you are trying to book stock our of a location where the product is not in stock.
This could be because the system defaults the location to the Default Pick Location of the product, if you have set this.
To view where the stock is actually located, click the unallocated tab and make sure the location you are trying to book out from also matches this:
Best before dates / batches!
If you have enabled best before date or batch code tracking, you will need to make sure you provide a matching value for these as well when booking stock out