A SPIFF is a short-term cash incentive paid on top of regular commission for selling a specific product, hitting a specific behaviour, or clearing stock inside a set window. It sits outside the main commission plan, usually runs for a few weeks, and is funded either by the seller or by the manufacturer whose product is being pushed.
The acronym has no settled expansion. Sales Performance Incentive Fund is the version most companies use, and plenty of others are in circulation. Nobody in a sales office has ever needed the long form, which tells you something about how the term is actually used: it means the extra money on this quarter's push, and everyone understands it without being told.
What distinguishes a SPIFF from the commission plan is time and specificity. A commission plan is designed to run for a year and to reward whatever the company wants sold in general. A SPIFF exists because something specific needs to move now. New product with no traction. Old stock ahead of a refresh. A competitor's renewal window opening. It is a tactical instrument, and the short life is the whole point, because a permanent SPIFF is just a rate change wearing a costume.
In hardware, telecoms and payments, SPIFFs are frequently funded by the vendor rather than the employer. A terminal manufacturer pays $50 a unit to the reps of the companies that distribute it. That money reaches the rep through their employer's payroll, which creates the accounting problem below and explains why so many SPIFFs get paid late, paid twice, or quietly not paid at all.
The design question worth asking before running one: what happens to everything the SPIFF is not attached to. Reps optimise hard against short windows, so a two-week push on one product reliably produces a two-week dip in everything else. A SPIFF large enough to change behaviour is large enough to distort it.
A rep sells six units of a new terminal during a four-week push. Their standard plan pays 8% of revenue. The SPIFF adds $200 a unit, funded by the manufacturer and passed through payroll.
The SPIFF is worth nearly double the commission, which is what makes it work and what makes it dangerous. At that ratio a rep will abandon a larger deal to close terminal number six before the window shuts.
A SPIFF is announced in an email, tracked in a spreadsheet by whoever proposed it, and paid through an adjustment line on payroll. It rarely reaches the commission system at all. Three months later nobody can answer which reps were paid for which units, the vendor asks for reconciliation before funding the next push, and the spreadsheet has an author who has since left. The fix is unglamorous: run the SPIFF as a dated rule inside the plan, with a start, an end and the same audit trail every other payout gets.
The long form lives in the guides: Commission structures.
Commish pays spiff the way your plan describes it, shows the arithmetic on every line, and traces each payment back to the deal that earned it.