You still sound very confused about your obligations and your client's obligations. It sounds like you expect to keep all your transactions under the radar and not declare any of them to any tax authority. Don't.
Just for this project in particular because of the complexity with sub-contractors. All other ones there isn't any issues because they are in-house.
You don't get to pick and choose which transactions you report to the government and which you don't based on how hard it is for you to bother with the reporting.