My husband and I married mid-year 2011. His taxable income is 4 times what mine is. Only a last half year of our combined incomes is joint income and the first half went to each of us individually. How should we split the very large income tax bill? Should we use the effective tax rate or the marginal tax rate to determine the tax liability on the latter half of the year, when we were married? It makes a huge difference. Thanks.