Solve Kasa · ESIRAwaiting Tax Administration approval

An online fiscal cash register, no dedicated device

Solve Kasa is an online fiscal cash register (ESIR) that runs in the browser – on desktop, tablet and phone – and issues receipts through the Serbian Tax Administration’s V-PFR. It is linked to inventory, the KPO book and the bank, and has an API for web shops.

Web shops
Order-based sales
Small shops and services
Accountants

Awaiting Tax Administration approval. The Solve Kasa application has been submitted and is under review. Until it is approved, the register must not be used for real sales and runs in demo mode only; demo receipts carry the notice “ОВО НИЈЕ ФИСКАЛНИ РАЧУН” (this is not a fiscal receipt).

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Leave your details and we’ll get back to you when the module is ready for real use.

Illustration with sample data · the app interface is in Serbian

receipts via the Tax Administration, no register hardware: V-PFR
of receipts, each as sale and refund: 5 types
receipt printing with QR code: 58 · 80 · A4
for web shops: API

Selling

A fiscal register built for speed

Made for the counter and for the phone: large buttons, shortcuts and everything on one screen.

Shortcuts and full screen

F2–F10 shortcuts and Ctrl+Enter to charge, plus a “Full screen” mode that hides everything else.

Several payment methods

Several payment methods on one receipt, with change calculated for you.

Discounts

A percentage discount on the whole receipt, with exceptions such as delivery, and per-item discounts as a percentage or dinars per piece.

Parked receipts

Park a receipt for later; an unfinished basket is kept on the device.

Barcodes

A scanner that works as a keyboard (USB or Bluetooth) or your phone’s camera. EANs are sent as GTIN.

Cashiers with their own PIN

Each cashier has their own account and personal fiscal PIN, and you can run a report for any period.

Receipts

Every fiscal receipt type in one place

Normal, advance, pro forma, training and copy

Each receipt type exists as a sale and as a refund.

Refunds

Full or per item, and never more than was sold. The refund copy has a signature line.

Advances

A chain of advances, closed with one advance refund and a final receipt showing the amounts paid in advance and the VAT on them.

Printing and sending

Print on 58 mm, 80 mm or A4 with a QR code, with automatic and test printing. You can also download a receipt as an image (PNG), or send it by email or as a verification link.

Software security element

V-PFR works with a security element file (PFX) and PAK. The register fetches tax labels and rates itself and warns you 30 days before the certificate expires.

Web shop API

A fiscal receipt for every web shop order

Your shop sends the order from its server, and the register issues the receipt with the same calculation as when a cashier rings it up. The API also covers refunds and a customer address book for filling in shipments.

Never two receipts for one order

Calls are idempotent per order reference (external_ref): a repeated request returns the receipt already issued.

Amount check

A receipt is issued only if the register’s total matches what the customer paid (expected_total).

Keys stored as a hash only

You see the kasa_… key once; only its SHA-256 hash is stored. Revoking it takes effect immediately.

Shop SKUs and stock

Link your shop’s product codes (SKU) to register items, so every sale updates stock.

Sample request from a web shop201 · receipt issued

POST /api/pos/receipts
Authorization: Bearer kasa_…
Content-Type: application/json

{
  "external_ref": "shop:order:1234",
  "expected_total": 4870,
  "items": [
    { "sku": "MAJICA-M", "name": "Majica", "quantity": 2, "unit_price": 1990 },
    { "sku": "SOLJA", "name": "Šolja", "quantity": 1, "unit_price": 890 }
  ]
}

The same external_ref returns the receipt already issued – never two receipts for one order.

Connected

A register linked to inventory, the KPO book and the bank

Inventory

Sales reduce stock, including raw materials by recipe, and refunds put it back.

KPO book

Bank

A single courier cash-on-delivery payout is matched to several fiscal receipts at once.

A tablet as the register

Pair a tablet with a QR code and it works as a device account that sees only the register.

Available today

What you can use while approval is pending

Import receipts from another ESIR

Import the fiscal receipts your current register issues as PDF: they go into your records and the KPO book and reduce stock.

Demo register

A trial account can get a demo register with a simulator: no real credentials needed, and receipts carry the “this is not a fiscal receipt” notice.

The “Register only” package

How it works

Fiscal cash register, step by step

Request a trial account
Try the register in demo mode, with no real fiscal receipts.
Tax Administration approval
If and when the application is approved, we contact everyone who left their details.
Security element and first receipt
Upload your security element (PFX) and PAK, and the register issues receipts through V-PFR.

Notes

Good to know before you start

Solve Kasa is under review by the Serbian Tax Administration. Until it is approved, the register must not be used for real sales.
The register needs a permanent internet connection through V-PFR. Offline operation (L-PFR) is not supported.
There is an HTTP API for web shops. There are no ready-made plugins for WooCommerce, Shopify or WordPress.
Receipts are printed through the browser’s print dialog, not directly over USB or Bluetooth. There is no link to card payment terminals.

Works on desktop, tablet and phone – installs like an app (PWA)

Open invoice.solve.rs in your browser and add it to your phone’s home screen. Nothing to download from an app store. The interface is in Serbian; invoice PDFs can also be in English.

Desktop
Tablet
Phone
Each company’s data kept separate
Hosted in the EU (Frankfurt)

Questions

Fiscal cash register: frequently asked questions

Is Solve Kasa approved by the Tax Administration?

Not yet. The application has been submitted and is under review by the Serbian Tax Administration. Until it is approved, the register runs in demo mode only and must not be used for real sales. We will announce it on this page when that changes.

Do I need a dedicated device?

No. The register runs in the browser on a computer, tablet or phone and issues receipts through the Tax Administration’s V-PFR. You need a permanent internet connection and a security element file (PFX) with its PAK.

Does the register work offline?

No. Solve Kasa works through V-PFR, the Tax Administration’s virtual fiscal processor, so it needs a permanent internet connection.

Can I connect my web shop?

Yes, through the HTTP API: the shop sends the order from its server and the register issues a receipt only if the amount matches. There are no ready-made WooCommerce or Shopify plugins, so connecting it takes a developer.

Can I already record receipts from another register?

Yes. Import fiscal receipts from another ESIR as PDF: they go into your records and the KPO book and reduce stock. In the Bank module, a courier cash-on-delivery payout is matched to several of those receipts.

Does the register support card payments?

You can mark several payment methods on a receipt, but there is no link to card payment terminals.

How much does the fiscal register cost?

There is no public price list yet. Pricing is agreed with each company.

How will I know when it’s ready?

Click “Notify me when it’s ready” and leave your details. We will contact you once the Tax Administration approves Solve Kasa.

Awaiting Tax Administration approval

Want to be the first to know when it’s ready?

Leave your details and we’ll get in touch once the Tax Administration approves Solve Kasa. Until then, you can try it in demo mode.

No commitment. We’ll get in touch when the module is ready for real use.