IR35 Customer

We are a construction company bringing in 2 external people for a contract running for 4 years. They are being brought in from a professional services company (not traditional agency company). Who determines their CEST as they are both Ltd company contractors. We pay the company for their time only.

Hi
If the workers are providing a personal service via their own intermediary, then IR35 rules may apply to the engagement.
As to who is responsible for completing the checks, depends on whether the end client is based in the public or private sector.
The only time the onus falls to the worker's personal service company, is where the end client/hirer is classed as a small company in the private sector.
In all other instances, the end client/hirer is responsible for completing CEST.
If you require any further assistance, please contact the IR35 Helpline on 0300 123 2326.