IF Statements, DATE and Excel

Here is the problem. I have a household budget, it is split into fixed and variable expenses. I would like to include the fixed expenses only during/after the month they are incurred.

Not a problem using the following lovely formula (using January as an example):

=IF((MONTH(TODAY()))>=1,Jan!A15,0)

[Where A15 = my fixed costs for the month].

But, the problem is that if I now go back an look at my 2014 budget all the fixed expenses have gone back to zero, as we’re now in January (or later) again.

What I need to do is tell the formula, that IF it’s later than Jan 2015 (or any given year) then use A15 otherwise 0, but I don’t know how to do it. Can anyone help?