Hi Jude,

Yes, as per nta notifications  any candidate belonging to ews category make changes in their form easily during the process of counsellings.

But right now you can opt its benefits under 85% state quota seats only and not under 15%AIQ seats(as per the official notifications).

So yes, at the time you are going to fill your counselling form online, you can change your category status from UR to EWS without any worries.

For more details you can check out the officoal sites for neet 2019 and nta.

Good luck.