Tenant has warned me that rent will be late this month, how should I manage this?

My wife and I have owned a rental property for just under 5 years now without many issues except for small repairs.  Our current tenants have had no issues for the past year since moving in, but just informed us that they will be late on rent this month (December 2025).  Their current lease runs through the end of June 2026.  There will be no issues from a cash-flow perspective for at least a month on our end, but I am now concerned about them being unable to pay at some point in December, and potentially falling behind in January too.  I am willing to provide them some leeway but also don't want them to decide they can just stop paying rent or fall multiple months behind.  I'm not running a charity here and the mortgage on the rental needs to be paid by my wife and I monthly, which we won't be able to sustain for multiple months without their rental payments.  If we get past mid-December without a payment, do I need to send some kind of warning?  Should I consider moving forward with eviction, etc?  What do I need to do here in Colorado to protect myself initially, and then to make sure I can get them out in a reasonable and timely manner if they do fall further behind in January?