SnelStart logo SnelStart automation · runs weekly

Create and send SnelStart sales invoices with AI

Every month you open Facturen in SnelStart Web, click through four steps per customer, and pick the same article again and again before you email each invoice.

Cotlet does it in your own SnelStart account with list_customers, search_articles, create_sales_invoice and issue_sales_invoice, called by your AI agent, an n8n workflow or a script.

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Hosted · nothing to install or maintain

Can SnelStart do this on its own?

SnelStart has a B2B API for software partners (checked 14 Oct 2026). You request a development key, and a production integration needs certification, OAuth, a webhook and five named customers. The endpoint list is visible only in the portal, and there is no official MCP server.

How you do it in SnelStart today

  1. Open Facturen in SnelStart Web and click + Nieuwe factuur. Pick the customer in step 1, or click + Nieuwe klant if the customer is new.
  2. Check the invoice date, delivery date and payment term in step 2 and click "Dit klopt zo".
  3. In step 3 enter Aantal and pick the article in Omschrijving. Choose Inclusief btw, Exclusief btw or Btw verlegd in Btw-instellingen.
  4. Click "Tussentijds opslaan" to keep a concept, or "Verder gaan" to reach step 4.
  5. In step 4 click Versturen to email the invoice, or Alleen Opslaan. Repeat for the next customer; a concept left in the overview is easy to forget.

How to create and send SnelStart sales invoices with AI

Prompt

For each customer in this list, create a sales invoice in SnelStart with the hours and article I give you. Show me each concept first, then send it by email after I say OK.
  1. 01

    Resolve every customer

    list_customers matches each name from your list. Unknown names are reported back; create_customer runs only if you said new customers are allowed, and it stops on names shorter than four characters.

  2. 02

    Resolve the article

    search_articles finds the article for your hours. SnelStart needs an article on every line, even for services, and each article is tied to a revenue group, so a missing article stops the run before anything is saved.

  3. 03

    Save concepts only

    create_sales_invoice saves each invoice as a concept, which has no invoice number yet. The agent shows the lines and totals so you can compare them with your hours times rate.

  4. 04

    Send after your OK

    issue_sales_invoice emails each approved concept. SnelStart assigns the invoice number at that moment and attaches the UBL file automatically unless the customer card turns it off.

  5. 05

    Report what is left

    Concepts you did not approve stay in a list, and customers without an email address on the card are held, because Web can only email invoices to a filled-in address.

What you get back

Example data

Created 3 concepts from your list:
- Northwind Studio: 12 h x 95.00 = 1,140.00 excl. VAT, sent by email, invoice 2026-0412
- Bakker Logistics: 8 h x 95.00 = 760.00 excl. VAT, sent by email, invoice 2026-0413
- Van Dijk Design: 5 h x 95.00 = 475.00 excl. VAT, held, no email address on the customer card
Sent: 2, held: 1

Other ways to ask

  • Create the invoices as concepts only and list them so I can review them in SnelStart.
  • Send the concepts that are saved but not sent yet.
  • Every first working day of the month, invoice the retainer customers on my list with last month's amount, reverse-charged for EU customers.
  • Create one invoice for Northwind Studio with these three lines and a 10 percent discount, and tell me the total.

What SnelStart allows, and what to know first

  • SnelStart Web needs at least one article to invoice, even for hours, and every article must belong to a revenue group (omzetgroep); revenue groups cannot be created in SnelStart Web, only in SnelStart 12.
  • A discount in SnelStart Web applies to the whole invoice, not to single lines.
  • The invoice number is assigned only when the invoice is emailed or printed, so a concept shows no number.
  • Emailing an invoice from SnelStart Web needs the customer's email address on the customer card, and a UBL file is attached automatically.
  • Self-billing invoices and combined invoices (verzamelfacturen) are not supported in SnelStart Web.

issue_sales_invoice asks for your OK by default. To run it weekly without you, switch confirmation off for that tool in your dashboard.

Sources: SnelStart Web help: Een factuur maken in SnelStart Web · SnelStart Web help: Een klant aanmaken in SnelStart Web · SnelStart: API for developers

Call create_sales_invoice from a script

curl

curl -X POST https://cotlet.dev/api/v1/snelstart/customers/cus_8f21/sales-invoices \
  -H "Authorization: Bearer $COTLET_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"vat_mode":"exclusive","lines":[{"article_id":"art_104","quantity":12}]}'

Example response

{
  "invoice_id": "inv_c_0041",
  "number": null,
  "status": "concept",
  "customer": "Northwind Studio",
  "vat_mode": "exclusive",
  "lines": [
    {
      "description": "Consulting hour",
      "quantity": 12,
      "unit_price": 95
    }
  ],
  "amount_excl": 1140,
  "vat": 239.4,
  "amount_total": 1379.4
}

MCP: add https://cotlet.dev/mcp/v1 with the same key; the call is snelstart_write → create_sales_invoice. Example data.

Schedule it in n8n, Make, Zapier or cron

SnelStart tools this automation uses

Cotlet SnelStart tools used to create and send SnelStart sales invoices with AI
Tool Parameters
list_customers query, limit, cursor
search_articles query, limit
create_sales_invoice customer_id, lines, vat_mode, discount_percent, order_reference
issue_sales_invoice invoice_id, action, email_text
All 14 SnelStart tools with descriptions

Frequently asked questions

Is it safe to connect SnelStart to Cotlet?

Yes. You sign in to SnelStart yourself, in your own Cloud Browser in the EU, and we never save your password. Your agents only get SnelStart once you enable it, every background request is listed, and the browser profile is stored encrypted with AES-256-GCM, the cipher 1Password uses for its vaults. The AI model never sees a login, posts and messages wait for your OK, and Disable for agents cuts access in one click. Independent scanners grade cotlet.dev A+ on Qualys SSL Labs, securityheaders.com and Mozilla Observatory; live results are on https://cotlet.dev/security.

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