PaySlate vs Invoice Ninja
Invoice Ninja is one of the best known invoicing tools on the internet, it is genuinely open source, and you can self-host the whole thing for nothing. We build PaySlate, so the bias is disclosed up front, and the places Invoice Ninja genuinely beats us are stated plainly below. Every claim here was verified in August 2026.
The most important difference is not a feature. It is where your invoices live. Invoice Ninja is a separate application, running either on Invoice Ninja’s cloud or on a server you maintain. Its WordPress plugin is a connector to that application, not an invoicing plugin: it imports products, exports customers, and offers single sign-on to the Invoice Ninja client portal. PaySlate puts the invoices inside WordPress, on your own domain, with no second system to run.
At a glance
| PaySlate | Invoice Ninja | |
|---|---|---|
| Where invoices live | In WordPress, on your domain | In the Invoice Ninja app (cloud or self-hosted) |
| Second system to maintain | No | Yes, if self-hosting |
| WordPress plugin installs | New (launched July 2026) | 100 active installs |
| Free card payments | Stripe and Square, with Apple Pay and Google Pay | Gateway support is broad on both hosted and self-hosted |
| Merchant of record for VAT and sales tax | Yes, via Paddle or Lemon Squeezy on Pro | No |
| Free tier limit | No client limit | Hosted free plan is capped at 5 clients |
| Cost | $79/year for Pro | Hosted from $18/month; self-hosted free, $40/year to white-label |
| Open source | No | Yes |
The architecture question decides most of this
If you are comfortable running a server, Invoice Ninja self-hosted is a serious piece of software and it costs you nothing but the hosting. You get the full Pro feature set in the self-hosted code. That is a real offer and very few products match it.
The cost is that invoicing becomes a system you operate. It needs a server, updates, backups, a database, and someone to notice when it breaks. If your WordPress site is already the thing you maintain, PaySlate adds invoicing to it rather than adding a second thing to maintain.
If you use the hosted version instead, the trade is different: your client clicks through to Invoice Ninja’s portal to pay. That works perfectly well. It is just not your site.
Cross-border tax
This is where PaySlate has something Invoice Ninja does not. On Pro you can route payments through Paddle or Lemon Squeezy, both of which act as merchant of record. They become the seller on the transaction and take on the VAT and sales tax registration, filing and remittance.
Invoice Ninja will happily calculate a tax line for you. It will not become the seller, and it will not file anything. If you sell across borders and that obligation is what worries you, that difference matters more than any feature list.
Where Invoice Ninja wins
It is open source and you can self-host it free. PaySlate is not open source. If software freedom or zero licence cost is your priority, Invoice Ninja wins outright and nothing below changes that.
It is a mature, complete business tool. Expenses, projects, time tracking, vendors, purchase orders, multi-user teams. PaySlate does invoicing and getting paid. If you want one system to run the whole back office, Invoice Ninja is doing far more.
It has years of production use behind it. PaySlate launched in July 2026. That is a fair thing to weigh.
Which one fits you
Choose Invoice Ninja if you want an open-source system of record for the whole business, you are happy to run it, and invoices living outside your website is fine.
Choose PaySlate if your website is already your business hub, you want clients paying an invoice on your own domain without a portal in the middle, and you want the option of handing your cross-border tax to a merchant of record. See pricing or the full feature list.