Thank you for reaching out to us.
Yes, you can remove this account.
But before removing this account from Azure, you will have to make sure, what is the role that is assigned to this account in Azure subscription. If this account holds the owner role, you can assign the owner role to any other account in Azure.
Also, make sure this account is not a service admin or an account admin for your tenant. If it is then you can change the service admin and then remove this account.
To remove this account from Azure AD, you will have to login to Azure portal with another account which has global admin or user admin role assigned. Once you login to Azure portal you can access azure active directory and delete this account.
For details on how to change the service administrator, you can refer article https://learn.microsoft.com/en-us/azure/role-based-access-control/classic-administrators#change-the-service-administrator
For details to check who is the account billing administrators, you can refer https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/add-change-subscription-administrator#determine-account-billing-administrator
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