Monthly limits are set by the IRS. For 2019, contributions for transit and van-pooling are limited to $265 per month. Parking contributions are also limited to $265 per month. Your monthly balance is carried forward and you can make adjustments to your contribution, join, or terminate plan participation at any time. Employer contributions are combined with employee contributions when determining maximum limits.
125 Plans/Commuter Account: How much can I contribute in a commuter account?