Usually when a tenant leaves a mess in a rental, I take it on the chin and clean it up, keep the full security deposit, and move on. They never leave a forwarding address anyway (if the property is a mess). The question is, if I wanted to account for and bill for the cleanup of the property, how should I estimate what to charge them?

I do the work myself. In this most recent case, I spent about two hours loading all the junk from the yard onto my trailer (it filled a 16 foot flatbed trailer) and will take it to the dump this weekend. Obviously there is the cost at the landfill, but how should I estimate the charges for unskilled work I chose to do myself?

I usually use approx of $25 per hour if I am doing something myself. Unless it's something like painting which I know the estimate cost for a pro so I use that. I am a very good painter as I did it a lot when younger so the quality of my paint job is par with a painter.

Also add any other expenses that you incur as well as the time it takes you to go to the dump and complete everything. I do not purposefully try to rack up as much as possible but I am also not overly frugal with these costs since that would require more of my time to find the right cheap labor. Tenants had the option of hiring someone or doing it themselves and they chose to leave it up to you.

They are always surprised by the cost to repaint a room as they only think about the cost of materials not the cost of hiring a painter. 

Read your state's Landlord-Tenant laws regarding security deposits. I don't believe you can charge ANYTHING for your time. @Jason C. I know TX is Landlord friendly. @Greg H. ?

The best answer I can give for Texas is to deduct what you are prepared to defend in small claims court if the amount was disputed(which is very rare)

Judges at the Small Claims level in Texas are elected officials and are seldom bound by precedent.  Some will allow you to deduct for your time and some will not

Personally, I always do

Thanks @Greg H. I have never tried to pursue it, because it seems like a judgement in Texas is about as valuable as a piece of scratch paper.

I either have tenants who take care of the property and get their deposit back or people who disappear in the night and I find out my unit is empty when I go there to ask about my rent money. The latter group have never gotten a dime back from me, nor have they had the balls to ask for it.

Originally posted by @Jason C. :

Thanks @Greg H. I have never tried to pursue it, because it seems like a judgement in Texas is about as valuable as a piece of scratch paper.

I either have tenants who take care of the property and get their deposit back or people who disappear in the night and I find out my unit is empty when I go there to ask about my rent money. The latter group have never gotten a dime back from me, nor have they had the balls to ask for it.

 Agree on the judgement.  However, I was referring to if a tenant ever challenged your deductions by taking you to small claims which is very very rare

Just document and throw into the file.  Keep in mind that in Texas, the 30 day clock to account for their deposit only begins when they surrender possession AND provide a forwarding address

I do not charge for my time, not allowed in any jurisdiction I know. I hire contractors to do work if I am out to stiff a really bad tenant. Tenants pay for all contractor fees.