If a timeoff type is enabled for a user, but no policy (that is, no accruals, resets and no effective balance is set for the type) has been set up, then, the user can book timeoff against that particular timeoff type.

However, the balance would start showing in negative values depending on the number of timeoff's booked against this timeoff type. This is because the initial balance would be zero as there is no policy set up for the particular timeoff type.