Add Finland regime by rilla · Pull Request #748 · invopop/gobl

rilla · 2026-03-01T18:14:54Z

Summary

Introduced new tax regime for Finland (FI) with the following VAT categories:
- standard (25.5%)
- reduced (13.5%)
- super-reduced (10%)
Added historical VAT rates (2013-2026)
Implemented Y-tunnus (Business ID) validation based on MOD 11
Added a B2B invoice example GOBL document
Added tests for all regime-specific logic
Corrections left undefined: Finnish VAT law doesn't restrict correction to specific document types, so GOBL's default permissive behavior applies
No supplier tax ID validation: Finland has a €20,000 annual turnover threshold for VAT registration (since 2025). Sellers below it aren't VAT-registered and have no obligation to include a VAT identification number on invoices.
Updated CONTRIBUTING.md to remove stalled references to deleted template and provide more detailed instructions for new regime additions.

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Requested a review from Copilot and fixed or dismissed (with a reason) all the feedback raised.
Requested a review from @samlown.

codecov · 2026-03-02T08:59:50Z

Codecov Report

❌ Patch coverage is 97.56098% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.11%. Comparing base (72beee4) to head (d23162a).

Files with missing lines	Patch %	Lines
regimes/fi/tax_identity.go	92.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #748      +/-   ##
==========================================
+ Coverage   93.09%   93.11%   +0.01%     
==========================================
  Files         368      370       +2     
  Lines       19624    19706      +82     
==========================================
+ Hits        18269    18349      +80     
- Misses        919      920       +1     
- Partials      436      437       +1

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Copilot

Pull request overview

Adds a new Finland (FI) tax regime to GOBL, including VAT categories/rates, Y-tunnus (Business ID) validation, invoice requirements, and supporting generated data/examples.

Changes:

Registered the new fi regime and added FI to the regime-code JSON schema enum.
Implemented FI VAT categories (with historical rates) plus FI-specific validation/normalization (tax identity + invoice requirements) with tests.
Added FI example invoice documents and generated regime definition data, plus updated contributor guidance and changelog.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`regimes/regimes.go`	Registers the new Finland regime via blank import.
`regimes/fi/fi.go`	Defines FI regime metadata and dispatches validation/normalization.
`regimes/fi/tax_categories.go`	Declares FI VAT categories and historical rate values.
`regimes/fi/tax_identity.go`	Adds Y-tunnus checksum validation logic.
`regimes/fi/invoices.go`	Enforces FI invoice supplier Tax ID requirements.
`regimes/fi/tax_identity_test.go`	Tests for FI tax ID validation and normalization.
`regimes/fi/invoices_test.go`	Tests invoice validation requirement and date-based VAT calculations.
`examples/fi/invoice-fi-fi.yaml`	Adds an FI invoice example input document.
`examples/fi/out/invoice-fi-fi.json`	Adds generated JSON output for the FI example.
`data/schemas/tax/regime-code.json`	Adds `"FI"` to the schema enum list.
`data/regimes/fi.json`	Adds generated FI regime definition data.
`CONTRIBUTING.md`	Updates regime-addition guidance and references.
`CHANGELOG.md`	Notes the new FI regime addition.

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samlown

Very nice! Not much to change here. We just need to double check the situation with Finish Tax Identities to ensure a VAT ID is required for any invoice.

rilla · 2026-03-02T09:56:28Z

Thanks for the early review, @samlown, caught me in the middle of some final polish. I've addressed your (and Copilot's) comments and this is now ready for a final review.

samlown · 2026-03-02T10:24:58Z

Sorry! Too keen :-) I should have waited for the non-draft state! Just let me know when ready.

rilla · 2026-03-02T18:58:29Z

Since #750 has been approved, I've amended the historic rates definitions so they reflect effective dates. I've also removed invoices_test.go as that behavior will be covered in tax/rate_def_test.go once the fix is merged.

samlown

Excelent.

# Conflicts: # CHANGELOG.md

rilla · 2026-04-15T15:57:37Z

Hey @samlown, I've updated this branch with master and ported the regime to use validation rules.

Copilot

Pull request overview

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

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Copilot · 2026-04-15T16:44:56Z

+func validateTaxCode(value any) bool {
+	val := value.(cbc.Code).String()
+
+	for _, re := range taxCodeRegexps {
+		if re.MatchString(val) {
+			return validateTaxCodeChecksum(val)
+		}
+	}
+	return false


validateTaxCode uses a direct type assertion (value.(cbc.Code)), which will panic if the rules engine ever calls the test with a non-cbc.Code value (e.g., due to reflection/indirection changes). Other regimes defensively do code, ok := value.(cbc.Code) and return false when the assertion fails; mirroring that pattern would make this validator more robust.

Oh, I had this but lost it during a small refactor. Adding it back.

Copilot · 2026-04-15T16:44:56Z

+Both regimes and addons use a `switch obj := doc.(type)` pattern to dispatch normalization and validation to the
+appropriate handler based on the document type. See the `Normalize` and `Validate` functions in any existing regime for an example.


This section references a Validate function in regime packages, but there are no func Validate(doc any) implementations under regimes/ (validation is done via rules.Register(...) + rules.Validate(...)). Please update the docs to point at the rules registration pattern instead of a non-existent Validate dispatcher.

Suggested change

Both regimes and addons use a `switch obj := doc.(type)` pattern to dispatch normalization and validation to the

appropriate handler based on the document type. See the `Normalize` and `Validate` functions in any existing regime for an example.

Normalization in regimes and addons commonly uses a `switch obj := doc.(type)` pattern to dispatch to the

appropriate handler based on the document type. Validation is rule-based: regimes register validators with

`rules.Register(...)`, and validation is executed via `rules.Validate(...)` rather than a regime-level

`Validate(doc any)` dispatcher. See existing regime `Normalize` functions and rule registrations for examples.

Updated this section to reflect the current rules-based validations.

Copilot · 2026-04-15T16:44:57Z

+A minimal regime needs four files:
+
+- `<cc>.go`: declares the regime and defines its metadata.
+- `tax_categories.go`: declares tax categories with rates and, optionally, historical values.
+- `tax_identity.go`: implements tax ID normalization, validation, classification, etc.
+- `invoices.go`: implements invoice-level validation (e.g. supplier must have a tax ID).
+
+Depending on the requirements you may also need:
+


The guide says a minimal regime needs an invoices.go file, but there are no invoices.go files in regimes/ (invoice rules, when needed, are typically in files like bill_invoices.go, and some regimes have no invoice-specific rules at all). Please adjust the wording to make invoice-level validation optional and/or align the filename guidance with the existing convention.

Suggested change

A minimal regime needs four files:

- `<cc>.go`: declares the regime and defines its metadata.

- `tax_categories.go`: declares tax categories with rates and, optionally, historical values.

- `tax_identity.go`: implements tax ID normalization, validation, classification, etc.

- `invoices.go`: implements invoice-level validation (e.g. supplier must have a tax ID).

Depending on the requirements you may also need:

A minimal regime needs three files:

- `<cc>.go`: declares the regime and defines its metadata.

- `tax_categories.go`: declares tax categories with rates and, optionally, historical values.

- `tax_identity.go`: implements tax ID normalization, validation, classification, etc.

Depending on the requirements you may also need:

- `bill_invoices.go` (or another domain-specific file): implements invoice-level validation when the regime requires it (e.g. supplier must have a tax ID).

Amended this section to reference bill_invoices.go (adopted across many regimes) instead of invoices.go, and org_identities.go instead of identities.go.

rilla force-pushed the finland-regime branch 5 times, most recently from b8c8646 to 514fb69 Compare March 1, 2026 23:03

samlown requested a review from Copilot March 2, 2026 08:57

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Comment thread CONTRIBUTING.md

Comment thread regimes/fi/tax_identity_test.go Outdated

samlown reviewed Mar 2, 2026

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Comment thread regimes/fi/invoices.go Outdated

Comment thread CONTRIBUTING.md Outdated

rilla force-pushed the finland-regime branch 2 times, most recently from b7f3cfd to 3364e4c Compare March 2, 2026 09:44

rilla commented Mar 2, 2026

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Comment thread regimes/fi/tax_categories.go Outdated

rilla marked this pull request as ready for review March 2, 2026 09:55

This was referenced Mar 2, 2026

Fix inclusive Since comparison for historical tax rates #749

Closed

Fix inclusive Since comparison for historical tax rates #750

Merged

mountolive mentioned this pull request Mar 2, 2026

Feature: Add Panama (PA) regime #747

Closed

13 tasks

rilla added 2 commits March 2, 2026 19:54

Add Finland regime

8952754

Remove stale template references from CONTRIBUTING.md

121d648

rilla force-pushed the finland-regime branch from 3364e4c to 121d648 Compare March 2, 2026 18:55

samlown approved these changes Mar 3, 2026

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Merge main into finland-regime

bdfd431

# Conflicts: # CHANGELOG.md

rilla force-pushed the finland-regime branch 2 times, most recently from 28c7ddb to 567561d Compare April 15, 2026 15:51

rilla requested a review from samlown April 15, 2026 16:39

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rilla added 2 commits April 16, 2026 08:56

Migrate Finland regime to rules-based validation

773c5cd

Update CONTRIBUTING.md for rules-based validation

d23162a

rilla force-pushed the finland-regime branch from 567561d to d23162a Compare April 16, 2026 09:25

		Both regimes and addons use a `switch obj := doc.(type)` pattern to dispatch normalization and validation to the
		appropriate handler based on the document type. See the `Normalize` and `Validate` functions in any existing regime for an example.

-Both regimes and addons use a `switch obj := doc.(type)` pattern to dispatch normalization and validation to the
-appropriate handler based on the document type. See the `Normalize` and `Validate` functions in any existing regime for an example.
+Normalization in regimes and addons commonly uses a `switch obj := doc.(type)` pattern to dispatch to the
+appropriate handler based on the document type. Validation is rule-based: regimes register validators with
+`rules.Register(...)`, and validation is executed via `rules.Validate(...)` rather than a regime-level
+`Validate(doc any)` dispatcher. See existing regime `Normalize` functions and rule registrations for examples.

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