<prompt> Human: Lets say a person has a high income - 155,000 per year. Max 2015 contribution amount to 401k is 18,000. So, 18,000 is 11.612903 of 155,000. When inputting what your percentage election is, my companys site wont take decimals. So, I can either do 11 or 12. 11 is 17050, which is 950 short of the max, and 12 is 18,600, which is 600 over the max.How can anyone perfectly max out a 401k? Do you have to go a little over and request the amount back before April 15th of the following tax year?  <response>: Most forms only let you use percentages. You can put enough to go slightly over and the payroll system will cut you off at the limit.Alternatively, most payroll systems will allow finer control than the forms and usually allow specific dollar amounts. Talk to HR or payroll. 