Making Tax Digital for VAT — VAT by API (HMRC)

Making Tax Digital (MTD) for VAT is the programme through which HMRC (His Majesty's Revenue and Customs, the UK tax authority) digitised VAT returns from April 2019. In practice: a business must keep its VAT records in digital form and submit its return exclusively through a software API, never again by manual keying into a portal. Crucially, MTD digitises the return, not the invoice — it is not an e-invoicing mandate.

History — from Making Tax Digital 2015 to the 2019 mandate

In 2015, HMRC unveiled the Making Tax Digital vision: modernise the UK tax system by replacing manual returns with digital records kept in accounting software, plus automated submission. VAT was chosen as the first workstream because it is periodic, structured and already heavily computerised on the business side.

On 1 April 2019, MTD for VAT became mandatory for all businesses above the VAT registration threshold (£85,000 taxable turnover). A soft-landing period first tolerated manual entries between spreadsheets, then imposed the digital link — an unbroken digital path from the data source to the API. In April 2022, the scope widened to all VAT-registered businesses, even below the threshold.

text mtd-vat-timeline.txt

2015       | HMRC announces the "Making Tax Digital" vision: replace manual
           | tax returns with digital records and software-driven filing.
           |
2019-04-01 | MTD for VAT comes into force: mandatory for businesses above
           | the VAT registration threshold (£85,000 taxable turnover).
           | Digital records + submission via MTD-compatible API.
           |
2020-04    | End of the soft landing period: end-to-end digital links
           | become mandatory — no more manual copy-paste between
           | spreadsheets.
           |
2021-04    | Deadline deferred (COVID) then confirmed: digital links
           | fully required for all affected businesses.
           |
2022-04-01 | Extension to ALL VAT-registered businesses, including those
           | below the £85,000 threshold — end of the optional regime for
           | small registered entities.
           |
2026+      | MTD for Income Tax Self Assessment (ITSA) rolling out from
           | April 2026 for the self-employed above defined income
           | thresholds. VAT remains the foundation.

Governance — HMRC

HMRC designs, operates and enforces MTD. It publishes on developer.service.hmrc.gov.uk a catalogue of REST APIs secured by OAuth2, and maintains a list of recognised "MTD-compatible software". Businesses never connect directly to an HMRC interface for VAT: they go through third-party software (Sage, Xero, QuickBooks, or bridging software for spreadsheet users) that calls the API on their behalf.

HMRC applies graduated penalties for non-compliance: a points-based penalty regime for late submissions since 2023, and fines for the absence of digital records or digital links.

Technical schema — MTD VAT API

The core of MTD is HMRC's VAT (MTD) API. The typical flow: the software authenticates via OAuth2, retrieves the return periods (obligations), then posts the return (returns) with the 9 standard boxes of the UK VAT form (Box 1 to Box 9).

Authentication — OAuth2 bearer token, header Accept: application/vnd.hmrc.1.0+json.
Fraud prevention headers — mandatory headers identifying the device and client (HMRC anti-fraud).
periodKey — period key (e.g. 26A1) retrieved via the obligations endpoint.
9 boxes — vatDueSales (Box 1), netVatDue (Box 5), totalValueSalesExVAT (Box 6)…
finalised — boolean confirming the return is final before submission.

http mtd-vat-return.http

POST /organisations/vat/{vrn}/returns HTTP/1.1
Host: api.service.hmrc.gov.uk
Authorization: Bearer {oauth2_access_token}
Accept: application/vnd.hmrc.1.0+json
Content-Type: application/json

{
  "periodKey": "26A1",
  "vatDueSales": 12500.00,
  "vatDueAcquisitions": 0.00,
  "totalVatDue": 12500.00,
  "vatReclaimedCurrPeriod": 3400.00,
  "netVatDue": 9100.00,
  "totalValueSalesExVAT": 62500,
  "totalValuePurchasesExVAT": 17000,
  "totalValueGoodsSuppliedExVAT": 0,
  "totalAcquisitionsExVAT": 0,
  "finalised": true
}

MTD vs CTC e-invoicing

Dimension	MTD for VAT (UK)	CTC e-invoice (continent)
Object	The VAT return	The invoice itself
Data transmitted	9 aggregated totals (boxes)	Full line-level invoice
Timing	Periodic (quarterly/monthly)	Continuous / real time
Channel	HMRC API + OAuth2	Platform/exchange + structured format
Format	JSON (totals)	UBL / CII / EN 16931
E-invoice mandated?	No	Yes (country-dependent)

MTD is a digitalisation of the return, not the invoice. The UK does not mandate B2B e-invoicing — it chose a path distinct from the European CTC model, which feeds the post-Brexit divergence from ViDA.

Adoption — timeline and scope

April 2019 — mandatory for the ~1.2 million businesses above the £85,000 VAT threshold.
April 2022 — extension to all VAT-registered businesses, adding several hundred thousand more small entities.
Bridging software — the many small businesses keeping VAT in Excel use bridging software that pushes spreadsheet totals to the HMRC API without changing accounting tools.
MTD for ITSA — self-employed income tax joins the regime gradually from April 2026, confirming HMRC's "tax by API" trajectory.

Common pitfalls

Believing MTD = e-invoicing. False: no invoice is transmitted to HMRC. MTD covers only the VAT return.
Copy-pasting an amount between spreadsheets. This breaks the digital link and is non-compliant, even if the final figure is correct.
Forgetting the fraud prevention headers. HMRC rejects or penalises submissions without the mandatory anti-fraud headers (device id, IP, software version).
Getting the periodKey wrong. The period key must be retrieved via the obligations endpoint; a guessed value is rejected by the API.
Using non-recognised software. Only "MTD-compatible" tools from the HMRC list can submit. A direct call outside recognised software fails.

Foundations

Standards

Flagship messages

Tools