Social Security provides disability payments to qualifying workers who suffer from total disabilities that leave them unable to work. The Social Security Administration calculates how much you receive in disability by looking at your work history, but it reduces the payment amount in some cases if you have other types of income. In particular, certain pension payments will result in a smaller Social Security disability check. Below, we'll take a closer look at these provisions and how they might affect you.

Disability and pensions
In most cases, those who are eligible for pensions won't see any impact on their Social Security disability benefits. The key question is whether you had to pay Social Security taxes on the earnings that allowed you to qualify for your pension. For private businesses and for many government jobs, earnings are subject to tax withholding for Social Security, and so any pension you receive will have no impact on your disability benefits.

Certain government employers, especially state and local government agencies, do not have to withhold Social Security taxes from their employees' pay. In those cases, the Windfall Elimination Provision can apply to reduce your Social Security disability benefits. Determining the exact amount of the reduction is complicated, as it depends on the number of years you've worked at jobs where you did pay into Social Security as well as the year in which you became disabled. However, the SSA does provide a table that gives the maximum possible reduction, subject to the overarching rule that your benefits will never fall by more than half the amount of your pension. For instance, for those becoming disabled in 2015, the maximum reduction is $413 per month for those who worked 20 years or less in jobs subject to Social Security taxes. Those who've worked for 30 years or more in a Social Security tax-paying job won't see any reduction in benefits because of the provision.

Spousal and survivor benefits
If you aren't disabled but your spouse is, then you might qualify for spousal benefits under Social Security disability. Those benefits aren't subject to the Windfall Elimination Provision, but a separate offset known as the Government Pension Offset can apply if you have a pension from a job in which you didn't pay into the Social Security tax system.

The calculations for the Government Pension Offset are a lot simpler that the Windfall Elimination Provision. Your Social Security spousal or survivor benefits will be reduced by two-thirds of your pension. In some cases, that can completely eliminate your Social Security check, as there's no maximum amount for the reduction.

The vast majority of people can collect a pension with no impact on their Social Security disability payments. For the most part, only those who worked part of their career outside the Social Security system will face questions about how big their monthly checks will be from Social Security disability.

This article is part of The Motley Fool's Knowledge Center, which was created based on the collected wisdom of a fantastic community of investors. We'd love to hear your questions, thoughts, and opinions on the Knowledge Center in general or this page in particular. Your input will help us help the world invest, better! Email us at Thanks -- and Fool on!