Click the Close (x) button in the document window. If you have edited the workbook since saving it last, Excel asks whether you want to save it.
Click the Yes button to save your changes; click Cancel to continue working in the document; or click No to close Excel without saving changes.
Excel closes the workbook.
INTRODUCTION
When you finish working on a workbook, you can close it with or without saving changes and continue to work in the application. If you have been working in a workbook and try to close it, Excel asks you whether you want to save the workbook before it closes.
TIP
Program Window
Make sure you click the Close button in the document window, not the program window. Otherwise, you'll close all the open workbooks in Excel.
TIP
Available Buttons
When Excel has no workbooks open, only a few buttons are available on the Standard toolbar. As soon as you create a new workbook or open a workbook, the buttons become available again.