The Tenant Fees Act 2019 introduced a cap on tenancy deposits.
If you're signing a renewal agreement then you would need to refund the tenants the difference between the existing deposit and the capped amount. If you're issuing a new fixed term contract through the OpenRent website then it will automatically tell you if you have to adjust the deposit amount.
But if you're keeping the same tenancy as before then you don't need to change anything for now.
We have really useful guidance on this here.