Countries will have to agree politically in the next five months on when they can tax digital profits, how the profits would be allocated, and the principles for a global minimum tax, if the OECD is to meet its timeline, a senior official said.

“This is an extremely complex project and the stakes are high. The interests are not necessarily aligned,” Pascal Saint-Amans, director of the OECD’s Center for Tax Policy and Administration, said at the Oxford University Centre for Taxation Summer Conference. A solution will be fraught with difficulty, he said.

A political consensus would be the precursor...