Being a QuickBooks person I am not an expert on Xero but I think they have similar arrangements.
First option as mentioned is to ask your client to invite you to be a ‘User’ with your own sign on and password. A former client of mine gave me access that way.
A better option might be to become a ‘Xero Partner’. If it’s anything like QuickBooks you are given yopur own free ‘Accountants’ version of Xero which when you client sends you an ‘Invite your accountant’ invitation their Xero will be listed in the Clients section of your Xero giving you full access.
Further advantages are free training and accreditation and again if it works like QuickBooks your clients Xero subscription can be billed to you at a discount which you choose or not to pass on!!
I am in the process of setting up this arrangement with Xero and here is my contact:
Marion Reid, Partner Onboarding Specialist
Phone: 01908 538507