What is a function 

To add a function, click on the cell you want to enter the formula, then select Formulas from the ribbon and click on Insert Function. This will open a window where you can select the function you require. Now you can enter the data into the function. 

In this example, we’re going to use the average function. To calculate the average amount of VAT. 

Enter in the cells that you want to calculate and end the formula with a bracket. It is really important to always close brackets at the end of every formula.