As with most things we purchase, those toner cartridges you keep on hand for your printer have an expiration date. Using toner after its expiration date has passed can have ill effects on your print jobs and the devices they’re used in. The most visible effect you can experience from using expired toner is poor quality for your prints. Over time, the consistency of the fine toner powder within a cartridge can change, clumping and turning lumpy. In this state, it’s more difficult for the powder to be fused onto the paper, which will result in poor-quality prints from your laser printer.
Using expired toner can lead to much bigger problems than print quality, although you won’t notice them nearly as easily. Some printer manufacturers have warranties for their devices that are voided by using toner cartridges after their expiration date. If you’re using an expired cartridge and a technical issue arises that requires service, repair, or even replacement of a device, if it’s discovered you’ve been using expired toner your warranty could be voided. This would leave you high and dry, without a functioning printer or coverage to fix or replace it.