Earlier this month I was paid a bonus between normal paychecks. When this happens, taxes/401k/all the rest are not taken out by my employer's accounting department. Instead, these expenses are factored into the next regular paycheck, and taken out of that. This makes the regular paycheck not so "regular" in amount.
Unfortunately, I didn't remember this when I set up my spending plan for this month. And the paycheck I had pegged for $500 became, in reality, more like $293.
Crap, crap, crap.
Time for some revamping of December expenses.