According to the constitution, to run for president a candidate must show that they at least have a school-leaving certificate that must be submitted to the electoral commission.

In 2015, Mr Buhari, a former military head of state, failed to present the relevant documents.

He said that if the electoral authorities needed the documentation, they should contact the military, where he had spent most of his career.

This time round he has again referred the election commission to the military - something that is causing an uproar on social media, and the acronym Waec - which stands for West African Examination Council - is trending in Nigeria.

Here are some of the memes doing the rounds:

????Something lite????????@ollygodspower

 Buhari claims his WAEC Certificate is with the military.

Military: looking for Buhari certificate ????

6:11 AM - Oct 26, 2018

Fefe ????@Itootok

 My president doesn't even have WAEC ????????????????????

6:20 AM - Oct 26, 2018

Last month, the police tried to stop a candidate for running for governor of Osun state, saying he had forged his qualifications, but the president stepped in and the vote went ahead.

Mr Buhari's main rival in the upcoming elections, Atiku Abubakar, has presented his credentials, which include a diploma in law from Ahmadu Bello University in Zaria.