Restricted unions promote further cooperation among Posts from a specific region. They are governed by Article 9 of the UPU Constitution and have an important role in coordinating and facilitating the functioning of postal services at the regional level.

There are currently 19 restricted unions, covering most of the world's regions.

Restricted unions can be established by member countries, or their designated postal operators, if the legislation of those member countries so permits.

Countries belonging to a restricted union may conclude agreements among themselves regarding international postal services. The provisions of these arrangements, however, must be as favourable to customers as those provided by the UPU Acts.

The UPU works with the restricted unions to develop and implement the world postal strategy through well-defined regional development plans.

During a series of round tables, regional postal stakeholders are invited to give their views on the draft world postal strategy. This approach allows the regions to decide on their own priorities while contributing to the overall strategy. Some countries, for example, give first priority to improving the quality of service, while others place postal reform or the development of financial services at the top of their agenda. The UPU is committed to improving synergies and strengthening cooperation with the restricted unions. It cooperates with them in many other areas, including that of technical assistance.