Business…
If an extinguisher is brand new, it needs to be visually checked monthly by the business owner. If the owner does not want to take on that responsibility, they need to have it serviced annually. Every 6 years a full servicing should be done, and every 12 years a hydro-static test should be done. It is often a better deal to buy a new extinguisher at the 6 and 12 year marks.
Residential…
There are no requirements for personal residences, but it is recommended that they be visually checked every year to make sure there are no cracks or rust and to make sure the pin is still in the green. After 10 years or so the extinguisher should be replaced.