Toner refilling commonly occurs several ways:

• Refilling and reuse by the end user. This is normally done by use of a DIY laser toner refill kit that includes a supply of compatible toner, reset chips where required, and instructions for the process of refilling. There are various types of toner powder, and many DIY toner refill products are available either online from ecommerce suppliers or through specialist retail stores.
• Refilling and resale by the original manufacturer. It is common for toner cartridges to be sold with reply paid labels enabling them to be returned to the manufacturer for recycling and reuse.
• Refilling and resale by a third party. Many independent companies that sell toner cartridges refill and reuse the original manufacturer's cartridges which they typically obtain from recycling companies. This is generally considered legitimate if the original manufacturer's branding is removed from the recycled product.
• Refilling as a service. Many independent companies offer a refilling service where customers can bring empty cartridges to be refilled. Toner refill franchises have sprung up over the last few years. Such refill chains offer services for customers to bring their empty toner cartridge and have it refilled on site or exchanges with a ready filled toner cartridge.
• Toner Remanufacturing. Toner remanufacturing is similar to refilling with the exception that not only is new toner added to a cartridge, parts that ordinarily wear out are also reviewed and replaced as required.

Toner cartridges cannot be refilled indefinitely, because their mechanical parts (such as drums and rollers) eventually wear out and an electro-optical device (the drum) become depleted or scratched. Organizations refilling cartridges for resale usually clean and test each cartridge to ensure that it is fit for reuse and resale. While several sources offer empty inkjet cartridges to be filled with your choice of ink it is difficult to find brand new empty OEM laser cartridges. A further complication is that some models of laser print engines, like most inkjet printers, communicate with "chips" or fuses inside the toner cartridge which indicate that the cartridge is exhausted, whether or not it actually is. Some research is usually required to determine the feasibility of refilling a particular cartridge.

In general, DIY refilling requires opening the cartridge (which was designed to prevent such activity), refilling the toner and capping the opening that was made to gain access. Some cartridges can be disassembled (carefully, lest you dump the toner contents all over yourself). Others require a hole to be drilled; vendors sell a soldering-iron-based device that melts a ~15 mm hole in the plastic housing which is later closed with a plastic cap, or tape.

There are only a couple of critical things to be aware of: all toner is not the same formula (it's not just a matter of quality), and in some cases there may be separate additions of toner and "developer". Most kits sold by refill outfits include instructions for the particular type of printer or copier.

The following basic types of refill toner (differing mainly in particle size and fusing temperature) have been identified by one vendor while other refill vendors insist that each printer or copier model requires a unique type.

1. Apple, HP, Canon printers
2. Canon PC copiers
3. IBM/Lexmark Optra and similar
4. Epson EPL, NEC Silentwriter
5. Xerox and Sharp
6. Samsung and Lexmark Optra E
7. Brother

Kits are available to refill the 4 toner cartridges used by colour printers (cyan, magenta, yellow and black), or to fill a single cartridge. Kits include a reset chip where necessary.

Toner types should not be mixed as the cartridge and the printer may be damaged.

Effect of refilling cartridges on print quality and printer life

Refilling cartridges either by the end user, or as a service, is claimed by most printer manufacturers and toner remanufacturers to be harmful to both the quality and reliability of the prints, the cartridge as well as the life of the printers.

Refilled cartridges are more likely to exhibit poor performance when compared directly against remanufactured toner cartridge or OEM toner cartridge counterparts. This is sometimes seen when a newly refilled cartridge is first inserted into a printer but is more commonly found later on as refilled toner cartridges are more prone to mid-cycle failure even though adequate toner may still remain within the cartridge.

Companies and individuals that refill toner, however, indicate that in most cases that cost benefits of refilling can sometimes outrun the costs of buying new cartridges

Environmental reasons to refill cartridges

There are environmental benefits to refilling the toner cartridges of laser printers. The environmental impact of the toner itself is the same whether it is delivered in cartridges or by itself, but a single cartridge is reused several times, eliminating much of the impact of manufacture and distribution.

Toner cartridges are made from plastic and small amounts of other materials. The plastic in each cartridges takes approximately 3.3 liters of oil to produce. 4 liters of petroleum are also burned to manufacture one toner cartridge, releasing the equivalent of .01 metric tons of CO₂ into the atmosphere. Thus refilling rather than replacing a cartridge saves approximately 7.3 liters of petroleum and releases 0.1 metric tons less CO₂. Refilling also avoids discarding a spent cartridge into landfill, where it would take minimum 450 years to thousands of years for some parts to decompose

Safety considerations

Toner powder can be harmful if inhaled, leading to some safety risks when refilling toner cartridges.

Toner powder is not toxic but does need to be handled with care. Health and safety regulations must be considered when handling, transporting and storing toner powders.

Gloves should be worn when handling toner as well as a protective dust mask to prevent inhalation. Spilt toner should not be cleaned with a standard vacuum cleaner as it can become electrically charged and ignite a fire, and is so fine that it passes through filters and can escape into the room or the vacuum cleaner motor