Ranked by the provider's API Evangelist rating — the Kin Score is scored per provider, not per API, so every API of a provider shares its band. How the rating works →

Strong 5 Solid coverage with minor gaps

Candid Health Patient Collections APIManage patient invoicing, payments, refunds, and accounts receivable. Automates patient billing workflows a...66.2 Zoho InvoiceThe Zoho Invoice API allows you to perform all the operations that you do with the web client. It is built ...61.9 Procore Invoicing APIThe Invoicing API from Procore — 2 operation(s) for invoicing.60.3 Telr QuickLink and E-Invoicing APIRemote creation of QuickLink payment links and e-invoices with extra data fields, for merchants who collect...55.6 Flywire Invoicing APIREST API for the Flywire Invoicing Platform — contacts, invoices, credit notes and invoice payments for a c...55.1

Developing 19 Usable, with meaningful gaps to close

AccountsIQ Integration API 2.0The current AIQ SOAP 1.1 integration web service. 219 operations covering customers, suppliers, stock items...54.2 Pabbly Subscription Billing APIREST API for Pabbly Subscription Billing — 95 documented operations across customers, subscriptions, produc...53.2 Proactis Invoice APIRetrieve invoices from Proactis, receive them pushed to your own endpoint as they reach a configured status...52.5 HyperPay HyperBillHyperBill issues invoices and shareable payment links that collect payment through the HyperPay platform wi...50.9 Tabs Platform APIREST API for the Tabs revenue automation platform that exposes the core data model of customers, contracts,...50.7 Autopay Accounting APIThe Autopay Accounting API provides Autopay invoicing data to external accounting and ERP systems, enabling...50.6 AdvicePay APIThe AdvicePay REST API (v1.0.1) exposes the fee-for-service billing platform to integrators: admins, adviso...50.4 Deskera Books APIREST API for Deskera Books, the cloud ERP and accounting product — contacts, products, accounts, invoices, ...50.1 Coupa Invoicing APIThe Coupa Invoicing API provides RESTful endpoints for creating, updating, and querying invoices associated...49.9 Semble Billing & Payments APIGraphQL surface for practice finances — invoices, invoice payments and line items, account statements, prod...49.4 Spotnana Invoicing APIAPIs to manage invoicing.48.5 NMI Invoicing APIInvoice management endpoints47.2 Harvest API v2REST API for managing clients, projects, tasks, time entries, expenses, invoices, estimates, and users in H...44.0 GuestReady Invoicing APIThe invoicing API from GuestReady — 2 operation(s) for invoicing.43.9 Request Finance AP and AR APIThe Accounts Payable and Receivable REST API for issuing invoices, accepting crypto and fiat payments, runn...43.6 Cora APICora's transactional banking API for Direct Integration: registered boleto and carnê (installment) issuance...42.2 National Australia Bank (NAB) Gateway Payments APINAB's first-party merchant payments REST API platform (the NAB Gateway / NAB Transact developer portal at n...40.6 silvercar Invoicing APIContract invoicing and pricing actions40.1 FreeAgent REST APIRESTful API for the FreeAgent cloud accounting platform. Provides full access to invoices, estimates, conta...39.3

Thin 24 Limited public surface area

Billogram v2 APIRESTful JSON API for managing invoices (billograms), customers, items, credit invoices, payment sources, of...37.5 Outpost Merchant of Record APIREST API to issue proforma invoices for B2B customers paying by bank transfer, receive settlement webhooks,...35.9 Fresnel Software Invoicing APIThe Invoicing API from Fresnel Software — 42 operation(s) for invoicing.35.7 Hnry Platform APIThe REST API behind the Hnry app. It backs the Hnry iOS/Android clients and the published Hnry Zapier integ...35.3 Bakuraku APIREST API for the Bakuraku (バクラク) back-office suite. Publicly documented capabilities are retrieval and list...35.2 Zenskar APIZenskar's REST API for billing, contracts, usage metering, invoicing, payments, credit notes, and accountin...35.2 Fatora REST APIFatora's REST API for hosted-checkout payment collection, card tokenization, refunds and payment verificati...34.5 QuickBooksREST API for managing QuickBooks Online accounting entities including Customer, Vendor, Employee, Item, Inv...34.2 BillDesk CX+ Deep APIDirect REST API access for advanced payment processing, giving merchants full control over checkout UX. Sup...34.0 CyberSource Invoicing APICreates and manages payment invoices with customizable fields, due dates, and customer information. Generat...33.8 MakeLeaps APIREST API for the MakeLeaps cloud invoicing platform. Authenticated with OAuth 2.0 client-credentials agains...32.5 Taulia Supplier APIThe supplier-side integration API described in the SAP Taulia Description of Software Services. It exchange...31.5 FreshBooks REST APIREST API for FreshBooks providing CRUD access to clients, invoices, estimates, expenses, projects, time ent...31.2 FreshBooks Webhooks (Callbacks API)Event delivery surface for the FreshBooks Callbacks API. Subscribers register an HTTPS endpoint, complete a...31.2 Depositphotos Enterprise APIThe Enterprise API provides organizations with full content licensing workflows including searching 331M+ a...31.1 Exact Online REST / OData APIREST and OData API (v1) for Exact Online covering financials, sales, purchasing, inventory, HRM, CRM, proje...31.0 Cegid Click & Finance APIREST API for the Koalaboox / Cegid Click & Finance invoicing and invoice-financing platform. Resource-orien...30.1 NYISO Finance Invoicing APIThe Invoicing component of NYISO's Finance APIs, retrieving daily reconciliation data for both settlements ...28.2 Wave Financial GraphQL APIGraphQL API providing programmatic access to Wave accounting features including businesses, customers, invo...28.1 UNFI EDI IntegrationUNFI supports Electronic Data Interchange (EDI) for automated exchanges of purchase orders, invoices, and f...27.8 Accelo REST APIREST API for Accelo with CRUD access to companies, contacts, activities, tasks, projects (jobs), milestones...27.2 Zoho Invoice APIREST API for managing organizations, contacts, items, invoices, estimates, credit notes, recurring invoices...27.2 Holded Invoicing APIThe Invoicing API from Holded — 15 operation(s) for invoicing.27.1 Holded REST APIREST API for managing invoicing, contacts, products, accounting, projects, employees, and CRM records insid...27.1

Emerging 11 Early or largely undocumented

Fawaterak API v2REST API for the EasyPay/Fawaterak payment gateway. Authenticated with a vendor Bearer token, it lists avai...25.1 MyFatoorah Invoicing APICreate invoices and payment links.25.0 Geidea Pay by Invoice APICreate, update, fetch, delete, and send payment invoices (KSA) that customers settle through a Geidea-hoste...24.1 Geidea Pay by Link APIProgrammatically create, update, fetch, delete, and send (by email or SMS) shareable payment links so custo...24.1 Clear Books REST APIRESTful API for integrating with Clear Books accounting software to manage invoices, payments, contacts, ba...21.5 Novo PaymentsNovo money movement - invoicing, ACH transfers, and faster payouts (Express ACH). These capabilities are de...19.6 Found InvoicingCreate and send invoices, track their status, and get paid directly into the Found account, with invoice in...19.3 Heartland Bill Pay APIThe Heartland Bill Pay API enables invoice and bill payment processing for merchants accepting recurring or...14.6 Certinia Billing Central APIGlobal Apex service classes for subscription and usage billing. BillingService, BillingDocumentsService, Bi...13.0 VAT API v2REST API for EU and UK VAT compliance including VAT rate lookups by country, VAT number validation against ...13.0 UBS QR Portal APIA free programmatic QR-bill creation service supporting the Swiss QR payment standard. Returns QR bills in ...11.3

Minimal 5 Almost no public developer surface

CN eBillCN eBill is the customer tool for managing rail freight invoices, account statements, and online bill payme...9.2 ServicingLease and loan servicing covering invoicing, collections, portfolio management, and asset-level financial t...8.0 Knight-Swift EDI IntegrationKnight-Swift Transportation supports EDI integration for freight tendering, shipment tracking, and invoicin...7.4 LEAP Time & Billing APIModeled time recording, invoicing, and billing surface, evidenced by LEAP's own marketed "automatic timekee...6.4 xCBL — XML Common Business LibraryxCBL 4.0 is a royalty-free library of XML business documents and reusable components for business-to-busine...0.0

Companies reaching this through an API (35)

These companies publish an API, specification or operation carrying “Invoicing” but do not classify their business under it. Listed unranked and kept out of the count above, because one tagged operation is not a statement about what a company does.

Score breakdown

Frequency

64.6

log-scaled weighted occurrences

Breadth

3.9

spread across providers

Quality lift

36.6

mean composite of providers using it

Cohesion

23.0

strength of nearest seed neighbor

Where this tag sits

175 providers carry this tag directly, and 192 counting the 1 narrower tag below — 17 more to reach.

Accounting broader E-Invoicing 29 providers

Where this tag comes from

Provider tag178

Api tag64

Openapi tag5

Openapi op tag45

Markets provisional

Kin Score markets whose measured providers carry this tag. Share is the fraction of the market's measured providers that carry it — it describes the market, not this tag.

Market	Share of the market's providers
Accounting and Finance Ops	40%
E-invoicing and Tax Compliance (certified operators)	32%
Field Service, Home Services and Trades	27%
Billing, Subscriptions and Monetization	26%
Xero App Store (SMB finance, payroll, inventory and invoicing apps built on Xero, by region)	25%

Cohort brief

Auto-generated

The 175 providers in the APIs.io catalog tagged Invoicing, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers

175

all scored

Mean Kin Score

34.9

+12.7 vs catalog 22.2

Mean Agent Readiness

23.8

+11.8 vs catalog 12

Spread

0–84.5

median 33.1 · σ 16.5

How the 175 split by band

Exemplar 6Strong 15Developing 46Thin 56Emerging 42Minimal 10

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Contract Quality	35.5	17.2	+18.3	175
Developer Ergonomics	37.4	23.2	+14.2	175
Access Clarity	34.9	23.9	+11	175
Operational Transparency	22.7	13	+9.7	175
Discoverability	66.1	57.9	+8.2	175
Contract Governance	9.4	6.5	+2.9	175

A facet is averaged over the members that carry it, not over the whole cohort — the “Scored” column is that count. Averaging an absent facet as zero would score our own coverage gaps as the providers’ posture.

What this cohort publishes

Artifact	This cohort	Catalog	Difference
MCP server (any)	23%	13%	+10
MCP server (first-party)	24%	12%	+12
Agent Skills	0%	0%	0
OAuth scopes	26%	11%	+15
Security	99%	98%	+1
Arazzo workflows	1%	2%	-1
Governance rules	21%	16%	+5

mcp_pct counts any mcp/ artifact including ones API Evangelist derived from the provider OpenAPI; mcp_first_party_pct counts only servers the provider publishes. Prefer the latter.

Top by Kin Score

1 Xero 84.5
2 Square 78.1
3 Stax 72.5
4 Slash 69.5
5 Lili 68.7
6 Resolve 67.6
7 Monite 66.3
8 Tradeshift 64.8
9 Visma 64.7
10 Solvimon 60.7

Work with this as data

Every tag here is available over the APIs.io API and to AI agents over MCP.

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Tools for tags

7 MCP tools reach this

find_tagsBrowse and filter every tag in the catalog.
get_cohortThis tag as a scored cohort — every provider carrying it, with scores.
cohort_statsPRO — the distribution across this tag: mean, median, band split, adoption rates.
cohort_rankingsPRO — the leaderboard, on composite AND agent-readiness axes.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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The distribution (Pro)

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  -H "X-API-Key: $APIS_IO_KEY"

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Invoicing

Providers using this tag (175)

APIs with this tag (64)