Invoice Maker: Estimate & Bill

The build

Built for the people software usually forgets: plumbers, photographers, tutors, village shops. Full invoice lifecycle — estimates, tax presets, payment states, recurring billing — with zero network dependency, because the places that need invoicing most often have the worst connectivity.

What we handled

• Six professionally typeset PDF templates with logo & signature
• Payment state machine: Draft → Sent → Viewed → Paid / Overdue
• Recurring billing; estimates convert to invoices in one tap
• Reports export as CSV/PDF; private Drive backup, no account

Built for the worst connectivity, not the best

Invoicing apps are designed around offices; the businesses that need them most are standing in a workshop with two bars of signal. So the product rule was inverted: the network is the optional feature, never the dependency. Creation, numbering, tax math, PDF rendering and reports all run on-device — a shop can bill through a fibre cut, a blackout or a dead SIM without noticing.

That constraint shapes everything downstream: local storage is primary truth, sync is a background courtesy (backup to your own Drive folder when convenient), and the app's Play declaration — nothing collected, nothing shared — is again an architecture fact, not a policy choice. “We never see your business data” is a sentence a client's auditor can test.

Six templates that look designed, not generated

The PDF line is a typesetting engine, not a form fill: six layouts (Classic, Modern, Minimal, Bold, Creative, Professional) drawn through Flutter's canvas with the same tokens as the UI — logo placement, signature capture, line-item grouping, page numbering and currency alignment are laid out per template and tested against golden files. An invoice from Invoice Maker looks like a document a client received, not a receipt a machine emitted.

Because the renderer is code, customising “your” template for a paying business is a theme, not a rework — the same engine already produces the estimate and report document types, which is how one product covers quote, invoice and statement without three codebases.

A payment state machine, not a tick-box

Every invoice walks Draft → Sent → Viewed → Paid, with Partially Paid and Overdue as first-class states — the record of getting paid is the actual product, because chasing politely and on time is what small businesses lose money to. Payments are recorded by method (cash, bank transfer, card, cheque, UPI, COD) against the invoice, so balances stay true; recurring billing runs on the same ledger, generating weekly, monthly, quarterly or yearly documents deterministically.

Estimates complete the loop: quote a job, track acceptance or decline, and convert an approved estimate into a numbered invoice in one tap — the transition preserves the line items and snapshots the terms, so the document a client agreed to is the document that gets billed.

Tax, discount and currency as data

Custom tax rates with saved presets, percentage or fixed discounts, and 140+ currencies handled as first-class metadata mean the math adapts to a Dhaka shop and a Dubai freelancer with zero code change. Totals are computed from the same integer minor-unit engine as the ledger, so the PDF, the dashboard chart and the CSV export can never disagree — the reconciliation bugs that plague spreadsheet invoicing were designed out at the schema.

The dashboard reads that engine: revenue charts, paid/unpaid breakdowns, top clients and upcoming dues, all exportable as CSV or PDF for an accountant. No cloud BI, no seat licenses — a phone's worth of computation that fits a shop's reality.

The newest addition: scan toward an invoice

The current build's update note is blunt — “scanner feature”. The direction it marks: point the camera at a handwritten bill or an old invoice and have the line items pre-filled, editable before anything is saved. We ship auto-fill, never auto-send: the state machine above only advances through actions a human confirmed, because a billing tool earns trust by being wrong safely.

Free core, unlocks that don't hold the ledger hostage

The listing says free with in-app purchases, and the line we hold: the money-critical mechanics — unlimited invoices, states, taxes, exports — are the free core forever; unlocks buy conveniences and template depth. A business must never be locked out of its own records mid-month, which is also why backup files are plain, restorable and yours.

Launched weeks ago with a 0+ download counter, this page promises no viral numbers. What it does prove is visible in ten minutes of installing it: a document engine, a correct ledger and a release pipeline — the same three things your product would get.