The pivot. Seven migrations, 84 PHP files touched. The entire tenancy layer arrives: tenants core table (central registry), tenant packages (which plan each tenant is on), invoices, invoice line items, payments, gateway settings for local and international processors, dunning fields on invoices for failed-payment retry semantics. The SaaS migration plan document and the implementation shipped on the same day.
The dunning design is something I am particularly happy with: retry semantics and escalation policy baked into the schema at v1. Most billing systems retrofit dunning after the first batch of unpaid invoices causes problems. This one starts with it.
Eighty-four PHP files in a day is a lot. The entire payments subsystem, billing views, admin controllers, invoice status transition model — all wired and smoke-tested. This is the day Biznetrix became a SaaS product rather than a CRM.