BillFlow

What it is

BillFlow pulls time tracking data out of Monday.com, applies billable rates, and turns it into a PDF invoice you can send in one click. It runs as a native Monday app — no tab-switching, no CSV exports, no rebuilding the same spreadsheet every month.

How I got here

After building two Shopify apps I wanted to try a different marketplace. Monday.com caught my attention because the developer ecosystem is way less crowded — and when I started digging into the invoicing category, I found something kind of wild.

The best invoicing app on the Monday marketplace has 2,097 installs, zero reviews, and hasn't been updated since July 2023. The second-best has 372 installs. Also zero reviews.

Monday has a built-in time tracking column that every user gets for free. Agencies use it. Freelancers use it. But there's no path from "I tracked 14 hours this week" to "here's the invoice." The workaround is always the same — export, open Excel, manually add rates, format it, save as PDF, email it. Every billing cycle.

This isn't me guessing at a gap. There's a thread on the Monday community forum from December 2021 — a creative agency owner literally titled it "Create Invoice Based on Time Tracked in Given Period." It ran for three years. Ten replies. A Platinum Partner asked Monday if it was on their roadmap. The answer was basically silence.

Monday does have a native Quotes & Invoices feature, but it's CRM-only and has no connection to time tracking data. Users in the forums call it "too bare bones." The one competitor that tried to build this — Friday Billing — announced a beta in April 2024, offered free-for-life access to early testers, and then went quiet. Someone asked if it had launched in September. No reply.

I also looked at what exists outside of Monday. Tools like Harvest, Everhour, FreshBooks, Clockify — they all solve time-to-invoice, but none of them live inside your project management tool. Everhour is the closest — it has a Monday integration — but the #1 complaint is reliability. Disconnections, laggy timers, extension bugs. A native app wouldn't have those problems.

How it works

The app connects via OAuth, reads time tracking entries through Monday's GraphQL API, and walks you through a 6-step wizard. Pick a client and date range, review the hours, apply rates, customize line items, preview the PDF, and send it — or just download it.

Once an invoice goes out, those time entries get marked as billed. You can't accidentally double-bill a client. Void an invoice and the entries are released.

The interesting problems

Monday's time tracking API doesn't give you stable IDs for individual entries. If someone logs "2 hours on Design" on Tuesday, there's no permanent identifier for that specific entry. So I generate deterministic hashes from the entry content — person, date, hours, item — to track what's been billed across API calls.

The other thing I didn't expect: agencies organize their boards in completely different ways. Some use one board per client, some use groups within a single board, some use workspaces. There's no standard. So BillFlow has a configurable client mapping step during onboarding — you tell it how your boards map to your clients, and it works from there.

I also had to self-host on Railway instead of using Monday Code (their managed hosting). Monday Code has a 512 MiB RAM cap, no PostgreSQL, and a daily execution limit that would shut the app down mid-afternoon on a busy day.

Where it's at

Everything works end-to-end. OAuth, time tracking reads with pagination, the full invoice wizard, PDF generation with branded layout, email delivery via Resend, billed-entry tracking, client management, dashboard with status filters, and a settings view for company info, rates, tax, and payment terms.

What's left is marketplace submission — integrating Monday's native billing SDK, filling out the compliance pages, passing the Burp scan on the Railway domain, and writing the listing copy. Monday's review process is more collaborative than Shopify's (they create a shared board and work through issues with you), but the security requirements are more explicit — TLS 1.2+, HSTS, encryption documentation, data deletion within 10 days of uninstall.

This is the first app where the competition is essentially zero. People have been asking for this on the Monday community forums since 2021, the only competitor that tried appears to have stalled out, and the existing invoicing apps don't touch time tracking data. The bar is low enough that shipping something solid should be enough to own the category.