A second type of internal inconsistency occurs when the formula of the measured ion does not match the calculated mass. Often, a discrepancy arises because added atoms, such as [M + H] or [M + Na], have not been included in the formula. While the root of this error is primarily a matter of convention (see author guidelines above), there are strong arguments for stating the formula of the actual ion being measured in HRMS. Reporting only the molecular formula in cases of [M + H] or [M + Na] measurements complicates verification and invites errors, as it necessitates additional steps like adding atoms (or worse: adding the mass of atoms) to obtain the displayed calculated mass. The Python script identifies missing atoms and suggests a formula that fits the calculated mass (Figure , section b).