Range Naming Rules:
Begin with a Letter or Underscore:

Names must start with a letter or an underscore (_) and cannot begin with a number or any other character.

No Spaces:

Spaces are not allowed in names. Use underscores or capitalize the first letter of each word (e.g., Sales_Data or SalesData).

No Cell References:

Names cannot be the same as a cell reference (e.g., A1, B2).

Maximum Length:

Names can be up to 255 characters long.

Allowed Characters:

Names can include letters, numbers, periods (.), and underscores (_). No other special characters are allowed.

Unique within Workbook:

Each name must be unique within the workbook.

Worksheet Naming Rules:
Maximum Length:

Worksheet names can be up to 31 characters long.

No Illegal Characters:

Worksheet names cannot contain the following characters: \ / ? * [ ] :

Unique within Workbook:

Each worksheet name must be unique within the workbook.

Descriptive and Relevant:

It's best to use names that clearly describe the content or purpose of the worksheet for easier navigation and management.

Examples:
Valid Worksheet Names:

January

Financial Summary

Data Analysis

Q1 Reports

Invalid Worksheet Names:

January/2025 (contains an illegal character)

Budget*2025 (contains an illegal character)

Financial:Summary (contains an illegal character)


These rules ensure that names are compatible with Excel's internal operations and improve the clarity and organization of your workbooks.