Screenshot taken by Roger Cheng/CNET

Better late than never, Sprint is finally getting into the early upgrade game.

The company is preparing to launch Sprint One Up, a program that allows its customers to pay for their smartphones or tablets in monthly installments and upgrade after every year by trading in their devices, CNET has learned. One Up is slated to launch on September 20.

Sprint is the last of the national carriers to offer such a program, after T-Mobile kick-started the trend in July with its own Jump program. Shortly after AT&T launched NEXT, and Verizon introduced Edge. The moves underscore the increasingly competitive nature of the business, with each player looking to mimic its rivals.

A Sprint representative declined to comment.

All of the carrier programs principally work the same, with a few nuanced differences. Sprint's One Up lets customers pick up a phone with no money down and pay for the device in 24 monthly installments. A phone that costs $649.99, for instance, will cost $27 a month (with the difference tacked on to the 24th payment). If a customer leaves the service early, that person is on the hook for the balance of the device cost, due the following month.

After a year, a customer can upgrade to a new phone by trading in the device. A customer signs up for One Up with an Unlimited, My Way or All-In plan. One Up provides a $15 discount, which allows for an unlimited talk, text, and data plan that costs as little as $65 a month. T-Mobile's comparable unlimited plan costs $70 a month.

One Up is more like Jump in that it offers customers a break on the plan in exchange for the monthly-installment model. T-Mobile's Jump was seen as a better deal than AT&T and Verizon because the carrier previously knocked the price down on all of its plans when it moved to a no-contract model. AT&T and Verizon's early upgrade plans were criticized because they didn't offer any discount on the service plans despite requiring customers to pay the full price of their devices.

Screenshot taken by Roger Cheng/CNET

Existing customers who have been on contract for at least a year are also eligible, although the offer may be limited. Existing customers still on contract must trade in their existing phones, unless they are already up for a discounted upgrade. As with other plans, the existing phone has to be in good working order. Sprint prepaid customers aren't eligible for the program.

Sprint previously offered a little-known early upgrade program called "Upgrade Now," which required an upgrade fee. The program still exists for customers not eligible for One Up.