Almost none, because that’s highly unlikely for most people. The system is designed such that most tax-related things don’t need a return and end of year squari

Almost none, because that’s highly unlikely for most people. The system is designed such that most tax-related things don’t need a return and end of year squaring up. Income is taxed monthly by subtracting the correct amount. Interest is tax free to a threshold then has automatic withholding. Investments and savings can be held in tax-free wrappers with no reporting requirement. Benefits are paid outside of the tax system, etc.