Maintaining the Same Cell During Copy
This tip will allow you to "fix" a cell during a copy to prevent it from being shifted.
Note that this trick also works with cell ranges.
Example
In this example, the commission amount is calculated based on the turnover and the commission percentage using the formula:
=B2*B11

The result is correct.
Now let's copy this formula downwards:

You can see that there is a problem...
Looking at the formula in cell C9, we can see that both the turnover and the commission rate have shifted (which is quite normal):

To maintain cell B11 during the copy, there are several possibilities.
First Possibility
This involves adding $ to the reference of the cell that should not be shifted, then the formula becomes:
=B2*$B$11

Cell B11 will then be maintained during the copy:

Second Possibility
Another solution is to rename the cell that should not be shifted.
To rename a cell, select it and then enter its name (where its reference is displayed), then press Enter:

The new formula is now:
=B2*commission
The result will also be correct after copying:
