How are the estimates used? Are they converted into _quotes_ that are stated to the client for pieces of work? What happens if you give an estimate, then 1 week

How are the estimates used? Are they converted into _quotes_ that are stated to the client for pieces of work? What happens if you give an estimate, then 1 week later you learn new information, then have a new more accurate estimate? How will your boss respond to the new estimate? It is possible your boss is saying estimate but really meaning "quote". Who owns the codebase? Does it belong to the client or to your boss? Is it in anyone's interest that the quality of the code be improved over time? There is a conflict between efficiency and accuracy of estimates. If accuracy is a goal, you can improve accuracy at the cost of efficiency by giving very high estimates, then working slowly if the task turns out to be relatively simple. The codebase sounds like a bit of a tar pit. You may be interested in reading Feathers' book "working effectively with legacy code". This describes patterns and tactics to use to get automated regression tests in place around applications, so that you can start to refactor confidently and add unit tests. You need time and support to work on these if the existing code is bad. It can be very slow going and hard work. If you cannot convince your employer to support some changes to start gradually improving code quality over time, you should look at options for alternative employment.