Start with your HR department, but you can always ask some of your co-workers to check their statements for the contact information on the plan administrator. Once you obtain the plan administrator's contact information be sure that they have your correct address and updated contact information for them to send you notices including the statements. You should examine your statements regularly to make sure that they are correct.
Hi Luis! You should be receiving statements from your 401K plan custodian. If not, call your company human resources department and ask for the custodian's name and contact information. You should be able to call them a get your account balance. You will also want to find out why you are not receiving a monthly or quarterly statement and get set up to receive them. I hope that helps.
I think it is important that you not only know the balance of your plan but also what investments are offered. This kind of question may indicate that you may not have been as vigilant as you should be regarding your 401k. Look at this as an opportunity to not only find out your balance but also to find out other important information. For example is your portfolio diversified and what type of fees are you paying.
Luis, Ditto on the above answers. Your HR person usually is the best contact point. Often, 401k sites are set up to allow you to opt out of paper statements in favor or online statements, and sometimes those opt outs are easy to do on accident. Also, if your plan is a pooled plan (your assets pooled with other employees for investment by a trustee, usually the plan sponsor) then the quarterly reports are not necessary, rather there is an annual report that gives everyone a balance. It usually comes out some time after the year end of the plan, sometimes quite a while after.