You can save more for retirement next year using tax-advantaged accounts, thanks to a boost in the maximum 401(k) contribution rate by the IRS. The maximum rate increases by $500 to $18,500, which is the first increase in three years. Those aged 50 or older can still contribute an additional $6,000 on top of that amount. This is good news, because a 401(k) is one of most potent tools in your retirement arsenal…