Completely balanced reactions are needed to ensure that all possible products (including byproducts) are present and that all reactant atoms can be traced to product atoms. Relatively few reports exist in the literature that aim to complete reaction structures, with notable recent approaches relying on transformers and Condensed Graph of Reactions (CGR). Here, in keeping with interpretability, a balancing algorithm is implemented that considers the atom balance between the RHS and LHS. When there is an atom surplus on the RHS, reactants, reagents and solvents that address this surplus are added to the LHS. Likewise, when there is an atom surplus on the LHS, compatible small help species are added to the RHS. Help species are taken from a library of compounds ranging from water to small carboxylic acids and alcohols. For instance, Figure contains an atom surplus on the RHS that matches acetic anhydride which is initially listed as a reagent in Reaxys®. Introducing acetic anhydride as a reactant creates an atom surplus on the LHS that can be balanced with a molecule of help species acetic acid on the RHS, thus properly balancing the reaction. In some cases, for instance in Figure , the atom surplus on the RHS is caused by an untraceable group that cannot be resolved by reactants, reagents, or solvents on the LHS. These reactions are erroneous, missing important species and are removed. In cases where multiple candidate species can meet the atom surplus on either side of the reaction, an atom-to-atom mapper (detailed in step 7) is used to identify the most suitable species. A more detailed visualisation of the balancing algorithm is given in the ESI Section S2.