The other lawyer gave a superb answer. If you are left without a K-1 from the "S" corporation, then you should put your return on extension and try to get the information so that you can file an accurate return. If you are unable to file an accurate return because the person in charge of the corporation's books and records refuses to cooperate, then you should file your return with your best guess of your share of the income and expenses, gains and losses,, and attach to your return an explanation of the problem. Of course you are well-advised to guess high on the taxable income you pick up so that there is less of a chance of an underpayment penalty.
Schedule K-1 must be provided to each shareholder on or before the day on which the corporate return is required to be filed (March 15 - unless a 6-month extension is obtained). You should plan on filing a 6-month extension for your individual return, which will give you an extra 30 days to file after the corporation extended due date.
If you still don't receive the K-1 after making several documented requests and the deadline passes on September 15th with no K-1, you should file Form 8082 to notify the IRS that you did not receive the K-1. A link to the instructions for Form 8082 is provided below.
619-881-2305. This response to your question is general in nature, as not all the facts are known. Please consult an experienced attorney to review all your facts to receive specific advice for your matter. Mr. Paul's response does not create an attorney/client relationship.