You are under no requirement to pay a fee
You are only processing personal data for the core business purposes. You therefore do not have to pay a fee to the ICO.
However, it is important that your organisation adheres to the principles of the General Data Protection Regulations and understands best practice for managing information. To help ensure you are complying with the GDPR, we have produced a range of training materials including practical toolkits, training videos and more.
Even if you are exempt, you may still wish to pay a data protection fee.