Open-source Harvest alternatives: Kimai, solidtime, Invoice Ninja and Sumhour

What can you install today, and what do you still run or buy to bill a retainer? Kimai installs today, and its Recurring budgets plugin (149 €) adds retainers on top. solidtime installs today, but its invoices need a paid Business licence and it documents no retainers. Invoice Ninja installs today and can split one invoice into instalments. Sumhour has retainers with rollover and overage in every plan, with nothing to add, but self-hosting opens with the public launch. If you must install today, start with Kimai.

Each project’s own site, pricing page and code repository checked on November 5, 2026, plugin prices included.

If you want to own your data or run the software yourself, there are good open-source tools for tracking time and sending invoices. They suit different teams. Kimai is a mature, configurable time tracker with invoices, extended through paid plugins. solidtime is a modern time tracker with desktop apps. Invoice Ninja is an invoicing app that also tracks tasks, and its licence lets you read the code but not compete with its hosted service.

Sumhour is for agencies that bill from their hours: approvals, invoices, retainers and fixed fees, payments and margin in one product, licensed under AGPL-3.0. The code goes public and self-hosting opens with the public launch; until then Sumhour runs as a hosted service.

Side by side

Prices exclude tax. Plugin prices are from the Kimai store, which does not say whether they are one-time. "Not documented" means we found nothing on the project’s own pages, not that it cannot be done.

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Which one fits

• Kimai if you want a proven self-hosted time tracker today and are happy to add plugins for what you need.
• solidtime if your team lives in a desktop timer and a free single-user plan matters.
• Invoice Ninja if invoicing and payment gateways come first and time tracking is a side task.
• Sumhour if you run billable projects for clients and want approvals, agency billing and margin in every plan.

Where the others are ahead

• They can be self-hosted today; Sumhour’s self-hosting opens with the public launch.
• Kimai and Invoice Ninja have years of use and large communities. Invoice Ninja offers more payment gateways.
• solidtime has desktop apps and a browser extension available now; Invoice Ninja has native desktop and phone apps.

Other comparisons

• Sumhour vs Harvest
• Sumhour vs Toggl Track

Sources

• Kimai: pricing, plugin store, repository, read November 5, 2026.
• solidtime: pricing, self-hosted plans, repository, browser extension, read November 5, 2026.
• Invoice Ninja: pricing, payments, repository and licence, read November 5, 2026.
• Sumhour plans: sumhour.com pricing.