The app-based lender confirmed it is expecting most of the fresh capital to come from existing investors.
The funding will be used to sustain the current rate of growth and support Atom Bank’s future expansion plans, according to a spokeswoman.
After launching mortgages last year, the digital bank said lending has since grown strongly – but declined to provide numbers.
In its first set of annual results reported in July, Atom bank said customer lending, including business loans, was at £99m at year end and had increased rapidly post year end.
Atom Bank partners with brokers to offer mortgages through its app.
Musician will.i.am has been hired by the bank as a strategic board adviser.