How do rent discounts affect taxes vs value

[Seth McGathey]

In one of the podcast episodes, I remember them saying that if you are trying to avoid raising rents too high on an existing tenant, you are better off renting at the full amount you can and then giving them a discount on the rent. The idea was that it makes your property more valuable. But I wondered how this affects taxes.
Do I report the full amount I am "charging" and then somehow show that I collected less due to the discounts?
Or do I just take a small hit on my taxes because I am essentially claiming that I am collecting more than I am?
Or do I only report what I actually collected and ignore the fact that I am "charging" more? 

An example. The rent is $1500. I give the tenant a $100 discount if they handle the lawn care/snow removal themselves. So I only collect $1400 a month but they technically are being charged $1500 with a $100 discount. 

Even this seems like it could be done in a couple of ways. I could collect the full $1500 and then return the $100 each month. But that seems like a lot of busy work. I could also just only collect the $1400. 

Thank you!