NAB has sacked 20 bankers and disciplined another 32 over after they sold mortgages without accurate customer information and documentation.

NAB says it reviewed its mortgage book and identified about 2,300 home loans sold since 2013 that could contain inaccurate information.

The problem loans were largely arranged in New South Wales and Victoria.

The bank says it is writing to about 2,300 customers to invite them to participate in a detailed review of their loan.

The review could include verification of documents submitted during home loan applications.

NAB says it may offer affected customers compensation as appropriate.

“What occurred was unacceptable,” said NAB's head of customer banking and wealth Andrew Hagger.

“We have investigated this matter thoroughly, and, as we have always said, whenever we find issues we will investigate them, fix

Investment bank UBS earlier this year calculated up to a third of Australian mortgages — about $500 billion worth — could be based on factually incorrect information.