If you use CBD oil, you should not test positive for cannabis on a workplace drug test. Our workplace drug tests are testing for the metabolite Tetrahydrocannabinol (THC) in cannabis, which is the major psychoactive in the drug.
UK regulated CBD oil contains either very low amounts of THC or none at all. So there is little chance you will test positive for THC after using CBD oil. But, when purchasing, it is imperative that you buy from a regulated seller. Also, you can check how much THC is in the product if they disclose laboratory results for their product.
If the oil does contain trace amounts of THC, this should fall below the cut-off levels of the drug test. However, if you have bought a product outside the UK, this could be a different matter. Some unregulated CBD oils can contain up to 5% content of THC. As a result, if used regularly, you could test positive for THC.