Checkbox integration: Fiscal check for online store
Checkbox is a software recorder of settlement operations. Integration means one thing: as soon as the payment gateway has confirmed the payment, the store itself creates a fiscal receipt with the order items and gives the buyer a link to it. The manager does not take part in this - so the chain does not break at ten o'clock on a Saturday.
The work here is not so much in the checkout call itself, but around it: repeated callback of the gateway does not have to create a second check, a refund entails a return check, the shift is closed with a Z-report once a day, and in case of communication failure, there is an offline mode with an hour counter.
The term is 8–15 working days. Before the estimate, we go through your checkout for free and divide the calculation methods into those that require a check and those that do not: in the tool store we measured on 07/31/2026, there are ten of them, in the underwear store - exactly two, and both without online payment.
8–15 working days, of which 1–2 are for verification of calculations
after a free audit
Price
30
Guarantee
days after project sign-off
8–15
Term of works
working days, of which 1–2 are for verification of calculations
payment confirmation by the gateway, not order creation
Check moment
tool shop: 10 payment methods, 4 delivery methods
Measured on 07/31/2026
lingerie store: 2 ways, both upon receipt — nothing to be taxed
Measurement 01.08.2026
36
Offline mode limit
consecutive hours and 168 hours per calendar month
30
Warranty period
calendar days after acceptance
Who it's for
Situations where this service delivers results
Scenario 1 of 5
You already accept the card at the checkout, and punch the checks with your hands
The most common condition. The payment works automatically, and the fiscal part is kept by the manager with the cash register application on the phone. This works right up until the first weekend, sick day or evening peak of orders. The integration removes the person from the area, where he only needs to press a button at the right moment.
We'll review your situation in a free audit
Scenario 2 of 5
There are several methods of calculation, and their rules are different
The card is taxed at the time of payment, the non-cash account is not taxed at all, post-payment is a separate conversation with the accountant. In the shop of professional tools from our selection of ways ten, in the shop of tactical equipment - five, including installments. Each extra script is not just a line in the checkout, but a separate branch in the checkout logic.
Scenario 3 of 5
There are more orders than one person can handle
Manual punching has a clear payback limit: as long as there are a dozen checks per day, it is cheaper to pay the manager. When there are a hundred of them, there are missed ones, punched twice and punched with the wrong amount - and each such check is then canceled with an explanation for the accounting department.
Scenario 4 of 5
You are preparing to launch online payment and don't want to do it twice
Smart moment. Fiscalization connects to the same gateway callback whose signature is verified during payment integration. Doing both tasks at once is cheaper than returning to the payment processor after six months.
Scenario 5 of 5
There is more than one cash register - points, warehouses, several FOPs
Then routing is added to the integration: according to which rule the order gets to a specific checkout. Most often, this is the method of delivery, the warehouse of shipment or the legal entity of the seller. The rule is described in words, and only then in code.
What's included
Complete list of work and what you get as a result
The cash register and cashier are set up under your store, the signature key is stored outside the code repository
The check is created when the payment is confirmed by the payment gateway, not when the order is placed
The order items — name, quantity, price, discount and tax rate — are included in the check, not the line "Order No."
Duplicate Protection: A repeated gateway callback does not create a second check for the same order
The buyer receives a link to the check - on the thank-you page and in the letter, if necessary in an SMS
A refund check, in full or in part, is associated with the initial payment transaction
Opening and closing a shift according to a schedule with a Z-report - the shift does not hang for more than a day
Offline mode: the check is issued from the reserve range of numbers and reloaded when the connection is restored
Notifications when the check has not passed, the shift has not closed, or the key expires
Journal in the admin: the fiscal check number, time and status are visible for each order
Run on the demo checkout before the combat launch and one live order with a return
Guarantee of 30 calendar days for completed works
When this service isn't right
What's not included — so there are no surprises at delivery
Registration of PRRO in the tax office and submission of forms is done on your behalf; we say what data is needed
Obtaining a qualified electronic signature for the cashier
Tax advice: whether your sales scheme falls under taxation, your accountant confirms
Subscription fee for the PRRO service and tariff conditions
Merchandise accounting, balances and excise stamps — a separate volume of work
Connection of payment gateways is calculated separately
Free check of calculations before fiscalization
Before writing the code, you need to understand what exactly is a settlement operation in your store. We go through the checkout as a buyer, look at all available payment methods and break them down into those that require a check and those that don't. Then it is checked with your accountant - and only after that it makes sense to talk about the term and amount.
What we measure
How many payment methods are actually in the checkoutIn the shop of professional tools, which we measured on 07/31/2026, there are ten of them, including installments from two banks and cashless with VAT. In the underwear store, measured on 01.08.2026, there are exactly two, both with payment upon receipt. These are two different volumes of work on fiscalization, and the difference between them is many times.
Which of them create a settlement operationOnline card - yes. Transfer to a current account based on an invoice - no. Post-payment depends on who receives the money and at what time, and we take this place for coordination with your accountant as a separate item.
What happens now after paymentWho punches the check, in which application, how many minutes it takes and what happens when the manager is sick. The manual scheme lives exactly as long as one person manages to maintain it.
Is there a nomenclature for the check in the order?The check requires the item name, quantity, price and tax rate. If there is only an amount in the order, the guide will have to be created - it is a separate line of the estimate, and it is better to know about it before the start.
How returns are processedA refund and a refund check are two different things, and they often have different times. Let's see if there is a status in the admin that describes a partially returned order.
Status of the payment partWhether the signature of the gateway callback is verified and does not come twice. Fiscalization inherits all payment problems, and adds the price of mistakes to them — an extra check from the tax office does not disappear by itself.
What you get
Breaking down your payment methods into those that require a check and those that don't.
The list of places that must be agreed with the accountant before the start of work.
Evaluation of works and term with division into obligatory and desirable.
A 20-30 minute conversation with you, your accountant, or both.
Timeline: 1-2 business days from when we receive the site address
Why is it free
After such a check, half of the requests for fiscalization turn out to be smaller than it seemed, and some of them are not necessary at all. It is more honest to find out before the contract than after.
What's next
After checking, we give an estimate for a specific list of scenarios. If it turns out that you do not need the check, we will say so.
Short form: your contact and site URL
Contract, act and 30-day warranty
Every project gets a written contract: scope, deadlines, amount, acceptance procedure. After delivery — act and invoice, then 30 calendar days of warranty.
Sole proprietor & bank transfer
The contractor is a registered sole proprietor. Payment by invoice with closing documents.
Rights & access — yours
Code, design and materials transfer to you after full payment. Domain, hosting, repository and analytics are registered to you.
Client portal instead of email chains
During the project you get access to a portal: contracts, invoices, acts and project status in one place.
European clients
Among our work — projects for Norway, Bulgaria, Moldova and Spain.
Verifiable numbers
Every case in the portfolio comes with a link to a live site and a technical measurement.
Audit first, then pricing
There is no price list on the site intentionally: the scope of the same work differs multiples between clients.
We say "no" when unsure
If the task isn't ours or the deadline is unrealistic — we tell you upfront.
What affects the price
Why two seemingly identical tasks are priced differently
Number of payment scenariosThe main lever. One card through one gateway is the base volume. Ten calculation methods, as in a measured tool shop, mean ten answers to the question "is there a calculation operation here" and several separate branches of code with separate checks.
State of the nomenclatureIf the order item already contains the name, quantity, price and tax rate, the check is collected directly from them. If there are no bets anywhere, the directory is started from scratch, and this is a few days of work that have nothing to do with the cash register itself.
Returns and partial shipmentsA full refund is one check. Partial return of two items out of five, and even after partial shipment, is a separate logic of communication with the initial operation. For stores with a high percentage of returns, this block adds significantly.
The number of cash registers and legal entitiesOne checkout — no routing. Two points or two FOP — a rule for choosing a cash register by warehouse, delivery or seller appears, and each such rule must be checked on a live order.
Payment integration statusIf the gateway callback is already processed correctly and the signature is verified, fiscalization is connected to the ready location. If the statuses of the orders are kept approximately, first you have to put things in order there - otherwise the check will be tied to an event that cannot be trusted.
Process steps
Transparent stages with approval at every step
Total duration:8–15 days
1
Verification of calculations
1-2 working days
We go through the checkout as a buyer, record all payment methods and divide them into those that create a settlement operation and those that do not. The output is a list of scenarios, based on which the estimate is calculated.
2
Fiscalization rule together with the accountant
1-2 working days
We write down in words what method of payment, at what time and for what amount the check is created. Disputed areas - post-payment, prepayment in parts, delivery in a separate line - we close here, not in the code.
3
Cash register, cashier, key, demo mode
1-2 working days
We set up a cash register under the store, put the signature key outside the repository, raise the demo cash register. We run the first checks on it, while the combat cash register is not yet activated.
4
Connection of payment with a check
2-4 working days
Gateway callback handler, idempotence by order number, collection of check items from inventory, queue with retries in case the cash register doesn't respond the first time.
5
Returns, changes, offline, notifications
2-3 working days
Return check linked to initial operation, schedule shift closure with Z-report, offline mode with hours counter, fiscal failure and key expiration notifications.
6
Combat launch and transmission
1-2 working days
Live order for a small amount with subsequent return, checking checks in the cashier's office, journal in the admin, going through scenarios with your manager and accountant.
Did not find your case?
Describe how it works on your side — we will tell you whether “Checkbox integration” fits and what it means in your situation. No brief and no call: one question, one answer.
Technologies & integrations
What we build on and what it connects to
Stack
Checkbox API
PRRO
webhooks of payment gateways
queue of tasks with retries
idempotent keys by order number
cron to change and Z-report
OpenCart 3 / 4
WooCommerce
Next.js
PHP
HTTPS + HSTS
Integrations
Checkbox
LiqPay
WayForPay
Fondy
monobank
Nova Poshta - cash on delivery
KeyCRM
1C / BAS
Telegram — notification of failure of fiscalization
GA4 is a purchase event
Integration via API vs. manual penetration into the checkout application
How this option differs from the alternative
Manual punching / box moduleOur approach
When the check appearswhen the manager opened the application; at night and on weekends - the next dayby payment event, at any hour
What is written in the checkoften one line for the entire amount is faster, but this is another documentorder items with quantity, price and rate
Retrying the gatewaybox modules do not always check this; the double is removedthe existing fiscal number is given, a second check is not created
Closing the shifthands; a forgotten change blocks the next checkaccording to the schedule, the Z-report is generated by itself
Loss of communicationthe check is not punched at all or is punched retroactivelyoffline mode with hour counter and notification
Volume growthtime costs grow in proportion to the number of checksa hundred orders a day is the same work as ten
Cases
Tasks and results in numbers — all metrics measured by us
online store of professional tools, catalog of over 6,000 items
Task
Show from which point manual punching of checks ceases to be possible: the checkout contains all common payment methods in Ukraine.
Solution
An OpenCart store with ten payment methods - card gateway, banking applications, installments from two banks, cashless with and without VAT, terminal, cash in advance - and four delivery methods.
Result
Measurement 07/31/2026: 10 payment methods and 4 delivery methods, catalog 6,486 pages of goods and 361 categories. First server response 671.2ms with 407.8KB markup. Critical Defect Found: Bare domain returns 301 on HTTP even though the certificate is valid. It is not visible from the site whether the payments are taxed here: the check lives in the cashier's office, and that is why we start with checking the calculations, and not with the code.
online store of tactical equipment with a catalog of more than 50,000 items
Task
Disassemble a checkout in which a regular payment and an installment payment live side by side: for a check, these are two different scenarios.
Solution
Shop on OpenCart 3 by Cloudflare: card gateway, card online, cash on delivery, cash on delivery, cashless payment and installments online with a separate event in dataLayer.
Result
Measure 07/31/2026: 5 payment methods, including online installments with your own event. The catalog has 54,302 products and 635 categories — the figure was confirmed by two methods with a difference of 0.4%. First response 413.8ms, full download 511.1ms at 421.5KB. Defect found: hreflang declared as uk-UA and uk-RU instead of ru-UA. Installment here is the case when the moment of the check is agreed separately.
online retail underwear store with a catalog of over 110,000 items
Task
Check the reverse case: a large catalog and advertising offices, and there is no online payment at checkout at all.
Solution
Store on OpenCart 3 with three language versions and a sitemap with 42 submaps. Delivery by Nova Poshta in three options plus Ukrposhta.
Result
Measurement 01.08.2026, passing a real checkout by a guest: exactly two payment methods, both - upon receipt, checked on all four delivery methods. Icons of payment systems are only in the footer of the site. The catalog of 115,456 product items according to standard search and 112,646 unique addresses according to the site map, a discrepancy of 2.4%. The conclusion for fiscalization is straightforward: while there is no card in the checkout, there is nothing to automate the check.
What we need from you
We can't start without this — best to prepare in advance
1Cash register data from your PRRO account: cashier, password and license key of the cash register.
2The cashier's qualified electronic signature and password is issued to you, not to the contractor.
3The accountant's decision: by which payment methods and at what point is the check created.
4Directory of the nomenclature with tax rates, and if you trade with excise duty — with the corresponding marks.
5Access to the site and admins with the right to install modules.
6Test order for a small amount to test the check and return at the combat cashier.
If something is missing — let us know, we'll help you gather it or do it as a separate task.
FAQ
Most frequently asked questions — with concrete answers
Do we really need PRRO?
This is not decided by the site, but by your sales scheme and accountant. The rules are set by Law No. 265/95-VR: the first group of simpliciters does not carry out settlement operations through the registrar, the second-fourth from 2022 they do so regardless of turnover. The key word is "payment transaction": payment by card on the website is, but transfer to a current account by invoice is not. Therefore, before work, we break down your checkout into payment methods and show which of them are subject to taxation. Then your accountant confirms this: we write code, not give tax opinions.
When should the check appear?
At the time of the settlement transaction, and not when placing the order. The difference is fundamental: the order is created when the buyer clicks "buy", and the money may not go through. Therefore, we hang a check on the callback of the payment gateway with the status of successful payment — the same call whose signature is checked when the gateway is connected. If you link a check to the creation of an order, you will have fiscal checks for payments that did not occur, and you will have to cancel them.
What if the callback comes twice?
Nothing, if idempotency is established. Gateways retries when they do not receive a 200 response, this is normal behavior and not a failure. The processor remembers the order number and the fiscal number of the already created check, and when called again, it gives it instead of punching a second one. Without this check, the store receives a duplicate check for the same amount, and has to clean it up with a return check and an explanation for the accounting department.
How does the buyer receive the check?
Electronically. The link to the check is on the thank you page after payment and in the order letter; if necessary, we add SMS. You don't need a printed ribbon of the online store - the service gives a receipt via a permanent link, and it can be opened from your phone. If you send the goods by courier and want to put a paper copy in the box, the receipt is printed from a regular printer as a document.
And if the payment is postpaid at Nova Poshta?
This is the most contentious point in all of fiscalization, and the honest answer here is "it depends." The carrier accepts the money from the buyer, and it comes to your account later and in the already totaled amount according to the register. At what time and for what amount to create a check, your accountant decides, and we make this decision as a separate rule: an event from the carrier, an event from the bank or a manual confirmation by the manager. We do not invent the interpretation of the norm - we implement what your accountant signed up for.
What happens if the Internet or the tax service goes down?
For this, there is an offline mode: the cash register issues a check from a pre-received reserve range of numbers, and when the connection is restored, the checks are automatically reloaded. The mode has a time limit — no more than 36 hours in a row and no more than 168 hours during a calendar month. Therefore, there is an offline counter in the integration with a notification: when the store is approaching the limit, you will learn about it from the system, and not from the tax office.
Why close a shift every day if the store is open 24 hours a day?
Because the cash register change cannot last more than a day — after 24 hours it must be closed with a Z-report, otherwise the next check simply won't make it through. For a store that takes orders at night, this means one thing: the closing and opening of the shift is scheduled during the quiet hour, rather than relying on the manager's memory. A forgotten shift is the most common reason why fiscalization "suddenly stopped working."
Why not deliver a ready-made module from the extension marketplace?
The box module closes the simplest scenario: one checkout, one payment method, a check for the entire amount of the order. It breaks down where the store has several payment methods with different rules, partial returns or product items with different tax rates. In the shop of the professional tool, which we measured, there are ten ways of payment - the box solution here will have to be completed exactly to the volume with which we start. If you really have one card and one tariff, we will say so: install the module, it is cheaper.
Who is responsible if there is an error in the check?
In front of the tax office, there is always a business entity, i.e. you. Our area is for the check to go with the data you provided: correct item, quantity, rate, amount, form of payment. Therefore, we take the nomenclature guide and the fiscalization rule from you in writing and fix it in the technical task before the work begins. We correct errors that have arisen on our part within the warranty period of 30 calendar days after acceptance.
How long will it take to connect?
8-15 working days. Checking calculations 1-2 days, agreeing the fiscalization rules with the accountant 1-2, setting up the cash register and demo mode 1-2, linking payment with the check 2-4, returning, changing and offline 2-3, combat launch and transfer 1-2. Sometimes it takes longer when the nomenclature with rates is not yet available and the directory has to be collected from the price list.
Send the address of the store and a list of payment methods that work for you.
In response, there is a breakdown of which of them require a fiscal check, a list of questions for your accountant, and an assessment of the work by stages. If you do not need a check, you will hear about it in the first email.
From measured casesMeasurement 07/31/2026: 10 payment methods and 4 delivery methods, catalog 6,486 pages of goods and 361 categories
There is no price list on the site on purpose: the same work differs several times over between two clients, and a “from” figure explains nothing in that case. First a free audit — we count your pages, duplicates and speed — then we name the sum and the deadline and fix both in the contract.