What is the due date for someone to receive their schedule k1 estates and trusts from the organization managing the trust?

If April 15 is the due date and I do not receive a copy of the Form 1041 Beneficiary's share of income, deductions, credits, etc. before April 15th. As the beneficiary how do I complete my tax filing by April 15th since I need the information Part III to complete my tax filing?