30% eligibility given previous work in The Netherlands
I‘m just starting a new position in The Netherlands after four years living in the US (am a US citizen). I had the 30% ruling in 2010 when I worked in Holland. Am I eligible to apply for it again if I meet all the criteria, but four years have passed since I last had it, or is there a five year period that must pass before I am eligible for it again?
You can get the 30% ruling again if you are an incoming employee i.e. recruited from abroad. It seems like that is the case. So you can apply again. Rules changed since 2010 though. Instead of 10 years the maximum term you can now get the 30% ruling is 8 years. This period will be reduced with the months you were working/living in the Netherlands before.
There is no 5 year waiting period. A waiting period would only be applicable if you would have had the 30% ruling before for the maximum term (your stay in the Netherlands was more than 10 years). In that case you must have been out of the Netherlands for even 25 years to be able to apply again. But that is not an issue here.
If you need assistance: https://www.expatax.nl/30rulingapplication.php.