There are a few ways to do this:
1) You can turn off that late notification sent to tenants from your Settings page, but this would affect all tenants. We do not have any setting to turn this off for just one particular tenant.
2) Another option is you could also remove the tenant's rental invoices. Each time the tenant pays you you would create an invoice in Innago for that payment and immediately mark it as paid.
3) One more option would be if the tenant is not going to use Innago at all (i.e. not submitting maintenance tickets, etc.) we could remove their email address completely from Innago.