Open Source Quoting Software
A quote is the first number a customer holds you to, so the document has to be accurate, on-brand, and easy to turn into a real invoice once it is accepted. In open source, quoting mostly lives inside invoicing platforms rather than heavyweight configure-price-quote engines, which suits freelancers and small businesses more than complex product catalogs with deal-desk approvals. This is a small but deliberately curated corner of the directory. What open source buys you here is control over the estimate itself - branded PDFs, your own tax and currency rules, and a clean path from an accepted quote to a paid invoice - on a server you run, with the client and pricing data sitting in a database you can export.
Crater
Open source invoicing app for tracking expenses, payments, invoices, and estimates
InvoiceShelf
Self-hosted invoicing app for invoices, estimates, expenses, and payments
SolidInvoice
Open-source invoicing for freelancers and small businesses with self-hosted or hosted deployment
Our picks
Three tools, all invoicing platforms that quote well; pick by stack and by how your clients accept.
Best quote-to-invoice workflow: SolidInvoice SolidInvoice is built around the estimate-to-invoice handoff, with one-click quote-to-invoice conversion, recurring billing, and multi-currency support using real money objects and per-client currency. Payments run through your own Stripe, PayPal, or other Payum gateways, so no card data touches your server. Built on Symfony and PHP, it self-hosts for free, exposes a REST API with token auth, and is MIT licensed, the most permissive option here.
Best client-facing portal: Crater Crater creates professional invoices and estimates while tracking expenses and payments, and adds a customer portal with Stripe payments so clients can view and settle online. It supports recurring invoices, multiple companies, custom fields on estimates, and white labeling of invoice, email, and portal themes. Built with Laravel and Vue, it self-hosts from release downloads or Docker and ships React Native mobile apps for Android and iOS.
Best for running several companies: InvoiceShelf InvoiceShelf is a self-hosted, multi-tenant option built for individuals and small businesses that run more than one company from a single install, with per-company books, member invitations, and custom roles. It creates invoices and estimates, tracks expenses and payments, and offers recurring invoices, a customer portal, and custom fields. Built on Laravel and Vue 3, it installs with Docker Compose over MySQL, MariaDB, PostgreSQL, or SQLite.
What to weigh before you quote from it
Be clear-eyed about what this category is: the open source options here are invoicing platforms that also produce quotes and estimates, not configure-price-quote engines with product rules and multi-stage discount approvals. For a freelancer or small business sending line-item estimates, that is usually exactly the right tool. If you sell configurable bundles with volume tiers and margin gates, test whether the estimate builder can express your pricing before you commit, because none of these is built for a complex deal desk.
The feature that actually matters day to day is the handoff from an accepted quote to an invoice. SolidInvoice does one-click quote-to-invoice conversion, and Crater and InvoiceShelf both create estimates alongside invoices with recurring billing, so the number a client agreed to does not get retyped. Look closely at template and branding control, since a quote carries your logo and terms. Tax and currency handling vary too: SolidInvoice models money as real currency objects with per-client currency, which matters if you quote across borders.
Because a quote holds negotiated pricing and customer details, treat hosting and data ownership as part of the choice, not an afterthought. All three self-host with Docker over a standard database, SolidInvoice exposes a REST API with token auth for wiring quotes into other systems, and the customer portals in Crater and InvoiceShelf let clients view and accept online. Confirm what you can export before you depend on any of them - structured client and line-item data, not just a stack of PDFs - so a growing quote history never becomes the reason you cannot leave.
Related categories
Frequently asked questions
Is this quoting software or invoicing software?+
Both, really. The tools listed here are invoicing platforms that also handle the pre-sale step: quotes and estimates, the pricing and terms a customer agrees to before any invoice exists. Dedicated quoting software leans harder on line-item logic and approvals, while these lean toward billing. For a freelancer or small business, having estimates and invoices in one system is usually a benefit rather than a compromise.
Can these handle complex pricing rules and discount approvals?+
Not really, and it is worth being honest about that. SolidInvoice, Crater, and InvoiceShelf produce clean line-item estimates, but they are not configure-price-quote engines with product configuration, volume tiers, margin gates, or multi-stage approval routing. If your deals need finance to sign off on discounts before a quote goes out, these will feel thin. For straightforward estimates that convert to invoices, they are a good fit.
How does an accepted quote become an invoice?+
That handoff is the core workflow here. SolidInvoice offers one-click quote-to-invoice conversion, so an approved estimate becomes a billable invoice without re-entry. Crater and InvoiceShelf create estimates and invoices side by side and support recurring billing for ongoing work. Test the conversion with a realistic quote, including taxes and discounts, to confirm the totals carry over exactly rather than needing a manual fix.
Can customers accept or pay a quote online?+
In two of the three, yes. Crater and InvoiceShelf both include a customer portal where clients can view documents, and Crater adds Stripe payments so an accepted quote can be settled online. SolidInvoice runs payments through your own Stripe, PayPal, or other Payum gateways, keeping card data off your server. Confirm the acceptance step matches how your clients actually approve work before you rely on it.
Do these support multiple currencies and tax rules?+
To differing degrees. SolidInvoice is the strongest here, modeling money as real currency objects with per-client currency, tax rules, and discounts, which helps when you quote across borders. Crater and InvoiceShelf both handle tax and multi-company setups, though you should test your specific tax scenarios. If cross-border quoting is central to your business, prototype a real multi-currency estimate before committing to any of them.
Only three tools here, is this category too small to use?+
It is small on purpose. Open source has few dedicated quoting products, so this shelf collects the invoicing platforms that genuinely do estimates well rather than padding the list. All three are actively developed and self-hostable, and the strongest fit depends on your stack: PHP and Symfony for SolidInvoice, Laravel and Vue for Crater and InvoiceShelf. A short list is easier to trial properly.
What should I be able to export to avoid lock-in?+
Look past the PDF. A safe exit means structured data: quote and invoice headers, line items, client records, taxes, and payment references, not just printed documents. All three self-host over standard databases like MySQL, MariaDB, PostgreSQL, or SQLite, which keeps the underlying records reachable, and SolidInvoice adds a REST API. Export a real sample before you depend on any of them, since a button that only dumps client names is not an exit path.