Excel will always carry out your commands perfectly, and in so doing, it will betray you. Here are the top 6 ways to debug and quality check. Happy auditing!
1. Verbalize the actions to be performed by the formula, then write them out on paper (or type them out). Make sure the Excel formula matches these actions perfectly.
2. Make sure that Inputs are inputs and not calculations or cell references
3. Double-click on the cell (or hit F2 on PCs) to show its components, color-coded
4. Hit Ctrl+~, and select cells individually to visually audit the precedents
5. Trace Dependents, Trace Precedents (via Formula Auditing menu)
6. Mathematically evaluate the component parts of a formula and make sure each is correct