Basic - Client added into sales only allow to key in service item

Reason:

It’s due to the client’s default sales type set to “Internal Invoice”

Explanation:

[Sales type : Internal Invoice] only served as billing without stock deduction.

Hence, it only can add in serviced based item.

This restriction is within application itself, there's no setting for that.

Solution:

Change to other default sales type.

Troubleshooting error prompt in sales invoice – “You can only add service item”