Income Taxes

Well that will be much easier to pay flat tax throughout the year based on the income.but there are changes in the income of an individual.in large companies one or the other can be bankrupted.....what if a company or an individual loses his job?what if a company expected to earn x amount is not able to earn that much and earns lesser....?what if a company is in loss...?what if the income structure changes...there are a lot of questions associated with it.they tooo will needed to be tackled.so its one and same thing.....