Rebates can change as often as every two weeks, though most manufacturers have at least a monthly rebate period. Problem is, no one wants to barely miss a higher rebate when buying a car, either by buying a few days too early or too late. What to do?

When I last bought a car, I did so at the end of the rebate period. A helpful dealer actually suggested filling out the initial paperwork that day, but then waiting until the first day of the following rebate period to complete it and take delivery, to see if the incentives changed. This way, they could file the paperwork for either rebate period, since there’s a short grace period for doing so.

As it happened, the factory-to-dealer bonus went up by $500, so I ended up paying $500 less. But the change could have gone the other way, and having begun the paperwork during the previous period would have protected me. (Or so I was told.)

Once the paperwork has been filed with the manufacturer, though, the deal is final. If the rebate goes up a day later, you’re out of luck.