Abstract Background Cardiovascular diseases are ranked as the number one cause of death in Serbia, and one-fifth of them present ischemic heart disease (IHD). However, the physicians certifying the cause of death have either not been adequately involved in how to complete a death certificate according to the current International Statistical Classification of Diseases (ICD-10) or due to a high level of administrative tasks sometimes fail to complete the process of death certification. That is why we aimed to investigate the garbage codes (GCs) and the effects of their redistribution on underlying cause of death (CoD) estimates for IHD for 2015 and 2020. Methods Data from Belgrade mortality statistics in 2015 and 2020 were used to describe the occurrence and redistribution of garbage codes (GCs), defined as unspecified or impossible causes of death. In order to redistribute GCs we observed the underlying, antecedent, immediate causes and other conditions that contributed to deaths. Redistribution was done by consulting GBD methodology for GC proportional redistribution. The ICD-10 code range for IHD is I20-I25. Results In Belgrade, 17% (4022/23663) and 20.9% (5818/27775) of the deaths were coded with a garbage code in 2015 and 2020, respectively. In 2015, 2102 deaths (10.7% of all well-defined CoD) were attributed to IHD, while in 2020, 1806 (8,2% of all well-defined CoD) deaths were attributed to IHD. Finally, we redistributed a total of 452 deaths (GC type 1 203.9, GC type 2 122.1 and GC type 3 126.2 deaths) and 572 deaths (GC type 1 250.1, GC type 2 110.9, GC type 3 210.7 and GC type 4 22) due to IHD in 2015 and 2020, respectively. These calculations indicate a total number of 2554 and 2378 deaths due to IHD in 2015 and 2020, respectively. Conclusions A more detailed analysis of local practices, as well as continuing medical education in the field of death certification, could be a step forward in the future process of decreasing the number of GCs. Key messages • Since the huge number of deaths was added to ischemic heart disease in 2015 and 2020, it is crucial to focus on a more reliable disease surveillance system including better coding practices. • A deep understanding of the garbage codes and their redistribution could significantly shape future decisions on factors contributing to ischemic heart diseases.