IF function to define over budget or under budget

I have manually put in the over and under without using the functions but I need to know how to use the function;

Good morning mrose,
IF functions are actually quite easy to use (though they can definitely get tricky!). As a basic introduction, IF functions have 3 criteria, the first being what you are testing for (So if A1 has a drop down that has both 1 and 2 as an option and you want B1 to say "yes" if A1 has a 1 in it, or "no" if A1 does not have a 1, you would put it as =IF(A1="1", "yes', "no"). The second criteria (after the first comma, or A1="1",) is the value you want to return if the first criteria is met. The third criteria is what you want it to return if the first criteria isn't met.

So, with your specific example, you will want to do =IF("total monthly amount> total monthly budget", "over","under").

thank you for your help