I’ve now run into the same problem twice at two different companies with my 401k. Most companies offer matching contribution but they do so on a per transaction basis so you need to be sure that you spread your max contribution over the 12 month period for the fiscal year.

For example, if you receive a 50% match on your contributions up to 6% you’ll likely receive that match only as money gets taken out of your paycheck and into the 401k.

If you earn a salary of $100,000 and decide to contribute 20% then you’ll likely max out sometime in October 100k *20% = $20,000. 20k/12 = $1666/month. However the max contribution for the year is $15,500 so you’ll lose out as your employer will stop making withdrawals AND contributions when you max out as $1,666 * 10 = $16,600 sometime in September or October.

The appropriate formula is to divide $15,500 by your salary to get the annual percentage contribution.

In some rare instances, I’ve encountered a couple of people that opted to have 50% of their salary deducted so they could quickly be done with their 401k contributions but unfortunately if this person maxed out in March or April they would not receive any matching contributions for the rest of the year.