The electoral commission's president said "persisting insecurity in some parts of the territory" would be a challenge to holding a "free, democratic and transparent" vote.
The announcement comes as rebels have advanced in the restive east of the African country, displacing tens of thousands of people from their homes.
President Felix Tshisekedi came to power in January 2019, succeeding Joseph Kabila after 18 turbulent years as leader.
It was the country's first peaceful handover of power.
Tshisekedi has already announced his intention to run for a second term, despite clashes over the results.
Other possible contenders could include Martin Fayulu, the runner-up in the 2018 presidential polls who claims he was deprived of a victory in the vote.
There has been no immediate announcement from former prime minister, Adolphe Muzito, and the ex-governor of the southern region of Katanga, Moise Katumbi, who are also seen as potential candidates.
Augustin Matata Ponyo, another ex-premier, has said he will run.
Ponyo last year went on trial on charges he embezzled public funds, but the constitutional court ruled it did not have the authority to judge him. The court's line-up has however now changed and has said it could try him.
In the DRC, the presidential poll is held at the same time as parliamentary, provincial and local elections.
The president-elect would then take office in January 2024.