'compulsory step' is correct and usable in written English.
You can use it to refer to something required to be done or a process that must be completed in order to reach a desired result. For example: Attending the introductory seminar is a compulsory step before enrolling in the course.
A calibration experiment is another compulsory step in a methodology of microclimate monitoring.
This compulsory step must be undertaken before translating our findings to a commercial or industrial scale.
Animal testing will, for the foreseeable future, be an essential and compulsory step in assessing the risk and regulation of chemical development, as various industrial sectors have different legal constraints placed upon them as consequences of registration and approval procedures worldwide.
Like the other decoy receptors for chemokines CXCR7 does not activate heterotrimeric G-proteins, a compulsory step for typical signal transduction of heptahelical receptors [8], [46].
This should be a compulsory step when using the antibody in matrix containing high levels of serum protein.
This is a compulsory step that could hinder the researcher and thus might appear as a limitation.
All these are compulsory phases and admission cannot be completed if any of these compulsory steps is skipped.
Computerized versions on the other hand lack overviews and have a compulsory step-by-step function.
Creating records and attaching data lineage information are the only compulsory steps of the depositing process.
In order to evaluate and to design adequate policy instruments, some authors recommend the cost-benefit analysis (CBA) as a compulsory first step.
A third limitation, which is not specific to the current study, is that fMRI signal on the medial wall can be blurred at the acquisition stage, due to voxel size and spatial smoothing applied to the fMRI data as a standard (and typically compulsory) preprocessing step.
