The Complete MergeNinja Walkthrough
This is the whole product, start to finish: from an empty account to a personalized letter for every customer who owes you money. It covers the same ground as our video walkthrough, including what the second run looks like, which is the part most demos skip.
The three pieces
MergeNinja has exactly three pieces:
- A data source: QuickBooks Online, Stripe, or an Excel/CSV file you upload.
- A Word template: a normal .docx with merge fields.
- The merge: which combines the two and emails you the finished documents.
Everything below is one of those three.
Step 1: Connect your data (read-only)
This walkthrough uses Stripe; the flow is the same for QuickBooks Online. If your data lives in a spreadsheet instead, you skip the connection entirely and upload the file with column mapping.
Click Connect, and you land on the authorization screen. It’s worth actually reading, because this is the part you should care about with anything that touches your financials: MergeNinja only reads. It can see customers, invoices, and payments. It does not touch your money, your customers, or your books, and if you disconnect, access is revoked at Stripe’s (or Intuit’s) end, not just ours. The full details, including exactly which OAuth scope each connection grants, are on the security page.
Approve it, and you’re redirected back with a live connection.
Step 2: Sync with filters
A connected Stripe account exposes five datasets:
- Customers
- Invoices: with a computed days-overdue value per invoice
- Subscriptions
- Payments
- Payment Summary: one row per customer per year, with their payment totals. That last one is year-end statements in disguise.
For this run, we want invoices. Click Sync, and before anything downloads you get a filter: instead of every invoice ever, pull just open ones, including past due. Then the table loads: names, amounts as real currency, dates as dates, and a DaysOverdue column already computed per invoice. This table is ready to become letters, which is the whole point.
Step 3: The template is just a Word file
There’s no trick here: the template is an ordinary .docx. Your fonts, your logo, your wording. The only special part is the merge fields («CustomerName», «AmountRemaining», «DaysOverdue»), which Word builds natively from the Mailings tab.
Build the letter in Word, upload it under Templates, and it’s available for any merge on this dataset.
Step 4: Run the merge
Pick the template from the dropdown and start the merge. It runs in the background: for a big customer list that’s minutes, not seconds, and you get an email when it’s ready instead of watching a spinner. When the email arrives, open the report and download the output.
What the output looks like
One document per row. Maria: $1,400, thirty-two days overdue. James: $890, twelve days. Different customer, different numbers, same letter, and nobody typed anything. If past-due letters are the job you came here for, there’s a dedicated guide for dunning letters.
One thing MergeNinja deliberately does not do: send those letters to your customers. The finished batch comes to your email, and you decide what happens next: print and mail them, or attach them to your own messages. Nothing goes out the door without you.
The second run is the point
Everything so far (connecting, uploading the template) was setup, and it’s done once. Next month, the job is: sync, then merge. Two clicks. The template is saved, the connection is live, and the data refreshes when you sync, so the numbers are current every time.
First run: about ten minutes. Every run after: about one.
Who it’s for, and who it isn’t
A straight answer on fit. MergeNinja is built for small businesses and bookkeepers who send batches of customer documents (past-due letters, statements, receipts, renewal notices) from QuickBooks, Stripe, or Excel.
It is not for everyone. If you need e-signatures, approval chains, scheduled automatic runs, or complex conditional documents, this isn’t your tool, and you’d be happier with something bigger. If you’re doing statement runs by hand in Word every month, this was built for you.
If that matches your job, you can create an account and try it free for seven days, no card to start, and setup really is about the ten minutes described above.