Here are some steps you can take to troubleshoot incorrect SUM results in Excel:

1. Check Cell Formatting:

* Ensure the cells you're summing are formatted as numbers. Text formatted cells with numbers might not be recognized for calculations.
* Right-click on the cells and choose "Format Cells." Under "Category," select "Number" if it's not already chosen.

2. Verify Formula:

* Double-check the SUM formula itself. Look for typos, extra spaces, or incorrect cell references.
* Make sure you've included all the cells you want to sum within the parentheses of the formula.

3. Identify Empty Cells:

* Empty cells are treated as zero by the SUM function. Review the range you're summing to ensure there are no blank cells interrupting the calculation.

4. Check for Circular References:

* Circular references occur when a formula references itself, creating an infinite loop that can lead to incorrect results.
* You can use the "Error Checking" tool (located on the Formulas tab) to identify circular references.

5. Examine Hidden Cells or Rows/Columns:

* If you suspect hidden cells or rows/columns might be affecting the sum, unhide them temporarily to see if they contain values that should be included.

6. Consider Number of Decimal Places:

* If your number format displays many decimal places, rounding errors might occur during the SUM calculation. Try changing the format to a fewer number of decimal places and see if the sum matches your expectation.

7. Address Text Values:

* Text values disguised as numbers can throw off the SUM function. Look for any cells containing numbers with leading apostrophes ('), which convert them to text. Remove the apostrophes to include them in the sum.

8. Review Data Validation Rules:

* If you have data validation rules restricting certain values, ensure they're not preventing valid numbers from being included in the sum.

By following these steps, you should be able to identify the cause of the incorrect SUM result and get your Excel sheet calculating accurately.