What happens to my employer match if I only contribute during part of the year?

With a standard per-paycheck match, your employer matches only the pay periods in which you actually deferred. If you max out your own contributions early and stop mid-year, you can miss matching dollars in the later paychecks, because there is nothing to match then.

Some employers protect you with a year-end true-up that recalculates the match on an annual basis and deposits any shortfall, but not all plans offer one. If yours does not have a true-up, spread your deferrals evenly across all 26 or 24 paychecks so you contribute enough each period to earn the match all year. Check your summary plan description or ask HR whether a true-up exists before front-loading your 401(k).