Choosing tax filing software · 2026

Choosing tax filing software for your accounting firm: a 2026 guide

You do not pick tax filing software on the nicest demo. You pick it on a handful of things that decide later whether the package fits your firm: where the client data sits, which tax types it covers, whether it links to your bookkeeping and your filing system, and what each return costs you. Below is the checklist to run through in 2026, with the specific question to ask at each point.

The checklist in short

  • Cloud or on-premise, and does it run in a plain browser?
  • Does the client data stay in the EU, and is there a data processing agreement?
  • Which tax types does it cover: CIT, income tax, VAT, dividend tax?
  • Does it link to your bookkeeping and to RGS, Nextens or AFAS?
  • What automation or AI is built in, and what does it do with your data?
  • Do you pay per return or a fixed per-user licence?
  • How are security, backups, and continuity arranged?

1. Cloud or on-premise?

Cloud means you work in the browser with no install. On-premise runs on your own servers, where your firm handles the updates and backups itself. For most small and mid-sized firms cloud is more practical: no installer, no version number to track, no licence server that goes down after a bad update.

The choice is not a free pass. Ask whether the package runs in a plain browser without plug-ins, and who is responsible for the updates. The wider trade-off is in the homepage section on the EU and privacy setup.

2. Does the client data stay in the EU? (GDPR and data residency)

"In the cloud" says nothing about where the data sits. It is an architecture, not a location promise. A tool can be fully browser-based and still route your client data through servers outside the EU. For an accounting firm that matters: you work with tax numbers, salary data, and company details of clients.

Ask each vendor three things: which region the hosting sits in, where any AI inference runs, and who the sub-processors are. Record it in a data processing agreement (Article 28 GDPR). On top of the GDPR, advisors often carry a professional or contractual duty of confidentiality. More on this on how we handle data.

3. Which tax types does the package cover?

A broad filing suite usually covers the bulk: VAT, income tax, corporate income tax, payroll taxes, and often dividend tax, with the related reporting. Work out which types you actually need and how often you file them.

Watch the edges. Specific requests and analyses often sit poorly in a suite, or not at all: the 30% ruling application with its cover letter, the fiscal unity CIT request, or an ATAD2 hybrid-mismatch analysis. That is where you add a focused tool to a suite. The three software types sit side by side in the comparison.

4. Links to your bookkeeping and to RGS

The step that costs the most manual work is turning the general ledger into the return. Ask whether the package reads your bookkeeping data and whether it works with the Dutch Reference Classification System of Financial Information (RGS). RGS is the standardised chart of accounts that translates a trial balance or annual accounts into a filing file.

Concretely: can the package import or export an RGS bridge file, and in which format? Nextens reads a .rgs file, AFAS an .xml file. A package that does not connect here forces you to retype figures, with the errors that brings.

5. Automation and AI add-ons

More packages now offer AI features. The question is not whether there is AI, but what it actually does. A model that reads a messy upload so you do not retype it is useful. A model that decides the figures or the tax qualification itself is a risk: the output is then not deterministic and hard to check.

So ask: does the AI set the amounts, or only read along? And where does the inference run? For the calculations you want fixed rules that give the same result every time, not a generative answer that can differ tomorrow.

6. Price per return or a fixed licence?

Two pricing models are common: a fixed licence (per user or per firm, often per year) or paying per return. For the full breadth at high volume a fixed licence usually pays off. For procedures you run only a few times a month, paying per item is often cheaper and easier to manage.

Work it out on your real number of returns per type. A fixed licence for a procedure you run eight times a year is rarely the cheapest choice.

7. Security and continuity

Ask about encryption of data in transit and at rest, about the backup policy, and about how long your documents are kept. Just as important: what happens if the vendor stops? Can you export your data, and in which format?

A tool that does not keep client data longer than needed limits your risk. At Lowkey, uploads are processed in memory and then discarded; one billing line remains, never the contents of the documents.

Where Lowkey fits

Lowkey is not a full filing suite, and does not aim to be. It is four focused tools that work alongside the filing software you already use. They remove one specific manual step rather than replace your whole filing process:

The math and the form-filling are deterministic code: the same input gives the same document every time. Where a model reads along, it only reads; it never decides the numbers. All processing happens on EU infrastructure. VAT returns, income tax returns, and the full corporate income tax return are out of scope: for those you need a broader suite, and Lowkey complements it for the procedures it covers poorly or not at all. See the comparison by type.

Two concrete examples

01

A firm with a suite for the breadth

An accounting firm with six staff handles its VAT, income tax, and CIT returns in a broad suite. Each year it adds eight fiscal unity CIT requests. The suite covers the CIT return, but not the formation request: Part A and Part B are typed by hand and then checked side by side for consistency. With a focused tool that comes from one input, for € 49 per document instead of an hour of typing and checking. The suite stays; only that one step disappears.

02

An expat firm with many 30% rulings

A firm that supports expats files around thirty 30% rulings a year. The application form and cover letter are not in their filing software, so they are drafted per client by hand. A focused tool produces the form plus letter from the same data, on the firm's own letterhead, for € 49 per document, and the client data stays in the EU. The firm checks, signs, and files itself.

03

From annual accounts to filing file

After closing the annual accounts, the figures have to go into the CIT return. Instead of retyping the general ledger, the RGS bridge file maps each account to RGS, with review points for the items the advisor should check. You download a .rgs file for Nextens or an .xml for AFAS. The first file is free per firm, then € 5 per file, excl. VAT.

Frequently asked questions

What should you weigh when choosing tax filing software?

Seven things: cloud or on-premise, where the client data sits (EU data residency and GDPR), which tax types it covers (CIT, income tax, VAT, dividend tax), whether it links to your bookkeeping and to RGS, Nextens or AFAS, what automation or AI is built in and what it does with your data, whether you pay per return or a fixed licence, and how security and continuity are arranged.

Does cloud software mean my client data stays in the EU?

No. Cloud is an architecture, not a location promise. A tool can run entirely in the browser and still route your client data through servers outside the EU. Ask each vendor where the hosting sits, where any AI inference runs, and who the sub-processors are, and record it in a data processing agreement (Article 28 GDPR).

Is Lowkey a replacement for my tax filing software?

No. Lowkey is not a full filing suite. It is four focused tools that work alongside the filing software you already use: the 30% ruling application, the fiscal unity CIT request, the ATAD2 hybrid-mismatch analysis, and the RGS bridge file that turns annual figures into a filing import file. VAT returns, income tax returns, and the full corporate income tax return are out of scope.

Is paying per return cheaper than a fixed licence?

It depends on volume. For procedures you run a few times a month, paying per return is often cheaper than a fixed per-user licence per year. For the full breadth of VAT, income tax, and CIT at high volume, a suite with a fixed licence usually works out better. Work it out on your real number of returns per type.

Create account

Lowkey works per document: € 49 excl. VAT for the 30% ruling and the fiscal unity, € 5 per RGS bridge file (first file free per firm). No subscription, no seats. You only pay when a document is produced. Drafting and reviewing is free.

The Lowkey tools Portal for firms ATAD2 hybrid mismatch 30% ruling self-service