Petty-cash control for field teams

A mid-size Brazilian contractor ran fundos fixos for crews on several sites. Site leads spent from a float. Photos of invoices piled up in WhatsApp groups. Finance reconstructed the month from screenshots. Reimbursements lagged because nobody knew which receipts were already paid.

They needed a closed system: only invited people, receipts stored with the expense, and a loop that could be followed from spend to payment.

Caixa Flow is the operations layer for that loop. An employee has a float (valor_base) and one active petty-cash fund at a time. They photograph an invoice, fill document type, number, supplier, category, and optional obra, then submit. When the period is done they request close. Finance approves or rejects each line, confirms the total, records payment. The fund archives; a new one can open.

Owners invite admins. Admins invite employees. A platform admin onboards companies. Everyone else stays out. Data is isolated per company. There is no public signup.

Four roles: platform admin, company owner, company admin, employee. Job/site registry with optional per-employee restriction. Payment history. Excel and ZIP exports for accounting. In-app notifications and email on fund close, confirmation, and payment. Receipts in a private bucket, cleaned up after a retention window. Password login, invite acceptance, password reset.

Security is layered: route proxy by role, layout guards, and Postgres RLS. Sensitive writes go through SECURITY DEFINER RPCs.

The MVP is not public self-serve signup or billing, not bank or PIX automation, not per-company custom categories, and not a native app. It is a responsive web product with the camera in the browser.