#contractors Startups & Tools

On-site invoicing for trade professionals has historically meant either juggling paper and pen or deploying expensive field service software built for dispatchers and managers. InvoiceKoi occupies the practical middle ground: a mobile-first invoicing app designed specifically for electricians, plumbers, builders, and other tradespeople who need to generate quotes and collect payments while standing on a jobsite. The product addresses a real friction point in small trade work. Currently, professionals create estimates, then travel back to an office to formalize them as invoices. InvoiceKoi compresses this workflow into a single tap, converting a quoted estimate into an invoice directly from the phone. Clients can sign electronically on the glass or the porch, eliminating the need to circulate paperwork after the work is completed. What distinguishes InvoiceKoi from general invoicing tools is its strict offline-first design. Trade professionals often work in areas with poor signal, yet the app lets users create and generate full PDFs even without connectivity. This removes a critical barrier to adoption in remote or rural areas. The feature set is deliberately lean. Saved client profiles automatically populate addresses, payment terms, and tax information. A price book stores standard rates, allowing technicians to build invoices without recalculating job costs. Payment collection is integrated: clients pay through Stripe links, and transactions record automatically. The interface prioritizes speed and mobile use rather than extensive customization. The business model reflects its positioning. Drafting invoices and creating estimates is free and requires no account, lowering the barrier to trying the tool. Sending unlimited invoices requires a paid subscription, and the company also offers optional card payment processing. A separate browser-based invoice generator exists as a free alternative for users who want to stay completely account-free. InvoiceKoi is available on Google Play and is in the process of launching on the iPhone App Store. The product is built and operated by a solo founder in Singapore. The appeal is clear: professionals who have been handling jobsite paperwork on napkins or through tedious back-office processing have a tool now explicitly built for their constraints. For small trade operations that find field service software bloated and enterprise-targeted, InvoiceKoi delivers the mechanics of professional invoicing without the overhead.