We lock a project once specifications are created after discussions and approval from you. You may only revisit the specifications within the small time window till development commences.
However, should you come up with a set of requirements after project has commenced, we shall encourage you to consider those as phase II of the project, which we shall undertake after implementing the finalised specifications. Phase II will be quoted as per its scope and after a retainer is paid for the extra charge, we commence work.
But if your requirements are to be included within the initial specifications after project commencement, then you will also be charged for any wasted time / work over and above the charge for implementing new requirements.
We encourage our clients to closely work with us during specification creation so as to avoid wastage of any work / hours. It is after all your money.