The airframer says the upgrade raises the MTOW to 78t, an increase of about 1t, providing around 150nm (278km) additional range.
The modification takes advantage of the A320's load-alleviation system, software which uses control surfaces of the wings - the ailerons and outer spoilers - to relieve structural loads during manoeuvring and gust turbulence.
While aspects of the load-alleviation function were originally introduced for a specific certification purpose, these subsequently became redundant. The software was removed, although the mechanical systems in the wing remained in place.
But Airbus has concluded that, with new software, it can use the load-alleviation system to increase the A320's payload-range capability.
"Wing-load alleviation evaluations took place earlier and have now been successfully completed," says Airbus single-aisle programme head of marketing Stuart Mann.
"This reduces the bending moment to allow us to cater for higher loads."
Airbus says the upgrade - available on later examples of the A320 as well as the A319-based Airbus Corporate Jetliner - will be offered particularly to operators of North American transcontinental routes and longer European charter sectors.