An accelerator is a step-up in commission rate after you cross quota. Below target you might earn 8% of what you sell; above 100% the rate jumps to 12%, and above 125% it might jump again to 15%. The idea is to keep top performers selling hard after they have already hit their number.
Here is how it changes the math. Suppose your quota is $1,000,000 and your base rate is 8%. Hitting quota exactly earns $80,000. Selling $1,300,000 with a 12% accelerator on everything above quota earns $80,000 plus 12% of $300,000, or $116,000. Without the accelerator, the same overperformance would earn $104,000. The accelerator added $12,000 for the same work.
Some plans include the opposite, a decelerator, where the rate drops if you finish well under quota. Others cap total commission, which is worth knowing before a huge deal lands.
For planning, accelerators make income top-heavy and unpredictable. Most of the upside arrives in the final quarter, once quota is behind you. The common mistake is assuming the accelerated rate applies to the whole year rather than only to the slice above target, and then overestimating what a strong year will actually pay. Read the plan document for the tiers, whether they are measured quarterly or annually, and whether the year resets your progress.