This is for @pilou’s benefit mostly because his work on fedeproxy is paid via a company based in France where CIR is a way to fund R&D activities. In a nutshell up to 30% of the salary can be reimbursed if the work done is R&D.
The company can declare this work to the IRS and get the corresponding amount the same year, no question asked. However… there may be questions asked a few years later and if it turns out the activities are not R&D or there is not enough evidence of these activities, the money will have to be given back. The IRS is quite flexible when this happens and payments can be scheduled over a decade, but it’s not a risk anyone want to take.
To prevent that from happening, the solution is to ask for a validation in advance (which is called a rescrit). It explains in detail what the project is about and why it is R&D. The CIR guide (2.4 MB) describes how to do that in detail but it does not provide an example to get inspiration from. Luckily I spent days over the past months to write such a document in the context of another project. I’m waiting for permission to share it publicly but in the meantime I’m happy to share it privately.