Thank you everyone - I don't think it is acceptable to charge outrageous fees, however I do want the rent when the rent is due and sometimes this is done through higher fees.
I have seen this URL and unfortunately Late Fees: No Statute. The reason I am asking is one of my tenants are consistently late. While it is written in his lease $20 per day late fee, I normally give them a break and cap it at $300, but I have found they are consistently being late and told them that I will start charging them $20 if they continue being late.
The tenant often avoids my calls and text messages and when I do get a hold of him, he says I don't have the full amount; I only have $700. Then I say to them "it's better that I have some rent money than none at all", and I will be by to collect it. When I show-up they always have $100 bills in cash (I do write them a receipt on the spot). It is often I get this amount between the 7th and 10th of each month, but then the remaining amount doesn't come until sometime later in that month or even the beginning of the next month. I once served them with a 3 day notice to pay on Dec 20, (yes right before the holidays) but didn't have rent for November yet. The very next day I received the full amount for November. That said, they were late again the next month as well, so I started charging the late fee.
Their lease is coming due at the end of July and I am not going to renew their lease. I think they know they need to move on to something they can afford. I want to ensure that my late fees are within the law (which it doesn't look like there are any for Colorado) and that I am charging the "Norm" for our area.
Thank you for your response as well; I am just trying to get out in front of this and be prepared for the next tenant.
Just because you can charge anything you want I want to do what is fair and reasonable. This is why I specifically asked what others are charging in the Denver metro area as I want to ensure I am in aligned with other landlords.