If the only payment service your firm will be providing is AIS, you can apply to register as a RAISP.
On 13 January 2018 providing account information services became a regulated activity. Providers of this service must be registered (subject to transitional arrangements for firms that were providing these services on or before 12 January 2016).
If you are intending to provide AIS alongside other payment services, you will need to become an authorised payment institution.
You can apply for registration as a RAISP now via Connect.
Further information can be found in Chapter 3 of The FCA’s role under the Payment Services Regulations 2017: Our approach.