To some extent you can do that of course, but not 100%. Fraud takes place regardless what you think happens or doesn’t happen, but what you can do it, is ensure you’ve got essential controls in place to mitigate the risk. If you think about it, there are some very easy controls you may implement to avoid fraud happening on low levels of the company’s structure. 

It is okay to have bonuses, but make sure:

1. The bonus is never a major part of the persons monthly salary or it creates too much incentive;
2. The salary in itself is enough for an average person, again for creating less incentive for someone to cheat with bonuses;
3. Someone on higher level monitors the basis for the salary and / or bonus as well and that it’s approved and compared to others.
4. Make sure the above really happens and is effective!

Physical security of goods:

1. Outside working hours have the goods in a safe place, under surveillance.
2. When working on the premises, ensure that everything moves only with proper papers, i.e. invoices or something similar and have at east two people check for the deliveries in and out, preferably at least one should be with responsibility over the assets, i.e. if something gets lost, they’re the one who you’d may ask for the value of the goods.

Check bank payments:

1. Bank payments should always be monitored at least 4 eyes, that is at least by two people.
2. I would even go as far and say that it’s not about monitoring the payments once they’re done, but making sure that payments are prepared by one and confirmed by someone else. The one preparing shouldn’t have the right to approve payments and vice a versa. Obviously the management mostly retains the right to do both, but that way the risk at least is only on top level.

Have you got all that implemented? If not, reconsider some of your controls and processes.