What is the difference between Delete UPI number and Deactivate UPI number?

Here’s the difference between Delete & Deactivate UPI number:
Once you delete your UPI number, you will not be able to receive money on that number. You can link the same number within 6 months (this period may change subject to regulatory guideline). After 6 months, it will be freely available for anyone to use.
Do note that your mobile number cannot be deleted. It can be unlinked from Tata Pay UPI. Also, your mobile number is not allocated to anyone even when it is unlinked from Tata Pay UPI. It can be linked again to Tata Pay UPI any time.

When you deactivate your UPI number, you will not be able to receive money on that number. You can reactivate the same number any time.