The importance of internal corporate planning for sustainable and dynamic development of an enterprise is significant, leading to the current focus on selecting planning mechanisms and tools, methods of digitalization of planning processes and the formation of such systems that ensure adequate response of the entire functionality of the enterprise to the challenges of the external environment. The authors in this paper utilized general scientific cognitive methods and EPC methodology (event-driven process chain), alongside questionnaires and economic analysis. The object of the study was the engineering holdings of Russia. The following results were identified: methodologies for developing an end-to-end planning system in the holding; the requirements and characteristics of the digital planning environment; a model of the planning system and its modification. The findings and results of the study are applicable for developing internal corporate planning frameworks based on digitalization and achieve greater planning depth, modify individual elements of the planning system considering industry specifics.