Your 401k is a fantastic alternative to social security when planning your retirement. The IRS allows you to contribute a certain amount to your 401k each year before paying taxes. This contribution is limited, but each year, the IRS recalculate it based on certain economic factors.The contribution is not applicable to taxesEvery year, you are allowed to contribute to your 401k before taxes are due. This contribution is written out of your taxes and is a great way to save money and drastically decrease your tax bill. The amount you can contribute depends on the year and your current age. It is made up of two parts: 401k contribution limit and a catch-up contribution. Those over 50 may submit both. Currently, the contribution limit is $16,500 and the catch-up contribution is $500.If you do not plan to spend your entire year's earnings, it is best to contribute the maximum amount to your 401k and save a bundle in tax breaks. Changes in the maximum amountOver the years, the maximum 401k contribution amount has grown from $7,000 in 1987 to $16,500 in 2011. For the past few years, however, the maximum contribution amount has not increased. Experts say that this is due to the currently low rate of inflation, which is not drastic enough to trigger any sort of increase. The IRS bases its increases on a price index for urban workers. The projected increase for 2012 stands at $17,000. The added $500 is not as drastic as some of the increases in the past, but it is certainly an improvement.Keep track of the maximum amount predictions in order to figure out how much money to put away for your 401k contribution. The 401k contribution is a fantastic way to save money and plan for your retirement. If you keep a sharp eye out for any increases in the maximum limit, then you are sure to benefit from this retirement option.