How long does a contractor have to bill you?

There is no deadline to send a bill. However, there is a statute of limitations to bring a claim. The contractor must bring this claim within 6 years of doing the work in order to be able to recover. If 6 years pass, the statute of limitations will expire. There are also other issues that you may want to explore with an attorney. For example, most home improvement contractors (depending on where the home is and who the licensing authority is) are required to be licensed and provide you with a contract in writing. Failure to do so has certain consequences for the contractor and his ability to charge you. I suggest consulting a construction attorney in your area.