Schedule K-1

What tax-reporting obligation is created as a result of receiving a Schedule K-1 (apparently the result of an investment option implemented by our investment advisor in our IRA account)?

Also, regarding the timing, what happens if the K-1 is received only a couple of days before the April 15th IRS tax return filing deadline (why does a major investment company send these out so late?), and the recipient's tax return has already been filed?

Thanks.