Estimating postdoc salary with "30% ruling" in the Netherlands and is postdoc a "scientific" position?
Normally PhDs and Postdocs from abroad would be considered for the 30% ruling, simply increasing your net salary by adding 30% of your gross salary to the net salary. Concerning the salary, normally it would be around 3.1k I have colleagues who are postdocs and their salary is in that range. HR can help you in estimating the net salary and after your friend employee, HR will handle the process of 30% Ruling after being accepted by the municipality.


  Dutch tax legislation provides a special facility for employees attracted from abroad who possess a special expertise that is scarce or cannot be found on the Dutch job market: the 30% ruling. Under this ruling, the employer can provide up to a maximum of 30% of the gross salary to the employee as a tax-free cost allowance`


For more details:https://www.utwente.nl/en/products-services/product/p339189/30-ruling#introduction

I hope that would be helpful.