Documentation — Addlify Finance (UK)

Interactive Finance Sandbox (DEMO)

Test MTD ITSA quarterly filings and VAT returns in your browser

Addlify Finance includes a fully featured interactive simulator directly on our homepage. This lets accountants, sole traders, and landlords test the Excel Add-in capabilities completely risk-free using realistic mock HMRC Developer endpoints.

How to Unlock the Sandbox

1Go to the homepage (addlify.uk) and scroll down to the **Interactive Sandbox**.
2Enter the VIP access code DEMO2026 or VIP2026 to unlock the panel.
3Click on the **Finance** tab to open the simulated Excel worksheet workspace.

⚡

Interactive Features: The sandbox includes session-isolated SQLite databases, an automated VAT Returns 9-box generator, cumulative MTD ITSA YTD updates, multi-factor authentication popups, and instant OneDrive backup simulations.

Getting started

Install the add-in, activate your licence, and start a free trial

Install Addlify Finance

Addlify Finance is a native Office Add-in for Microsoft Excel — desktop (Windows/Mac), web, and iPad. Two ways to install:

1Microsoft AppSource (recommended): open Excel → Insert → Get Add-ins → search "Addlify Finance" → Add.
2Sideload manually: download the manifest.xml from addlify.uk/api/finance/manifest.xml and load it via Insert → My Add-ins → Upload My Add-in.

Activate your licence

Open the add-in taskpane from the ribbon ("⚡ Addlify Finance"). On first run you'll see a registration screen.

Trial: click "Start 14-day free trial" — no card required. You'll receive an activation email at the address you provide.
Existing licence: paste your licence key. The key is emailed after purchase and shown again on your account page.

ℹ️ The licence key activates the add-in on up to N devices depending on your plan (Solo: 1, Pro: 2, Cabinet: 2 per seat, Enterprise: unlimited). Switching devices doesn't lose data — see Data & storage.

Connecting to HMRC

OAuth 2.0 authorisation via your Government Gateway account

Before you can submit MTD updates or VAT Returns, Addlify Finance needs an OAuth token from HMRC tied to your Government Gateway account.

1In the taskpane, click Connect to HMRC. A popup opens at tax.service.gov.uk.
2Sign in with your Government Gateway User ID and password. If you use HMRC 2FA, enter the code from your authenticator.
3Grant Addlify Finance access to the scopes shown (read/write self-employment, property, VAT, obligations).
4The popup closes and the taskpane shows Connected ✓. The OAuth token is stored encrypted server-side.

🔐 Tokens auto-refresh while you're active. If 18 months pass without a refresh, you re-authenticate (HMRC's hard-cap policy). The add-in tells you in advance.

Agent connection (for accountants & bookkeepers)

If you act on behalf of clients, sign in with your agent Government Gateway credentials. You'll be prompted to select which client(s) to authorise (by UTR or VRN). One Addlify Finance licence covers your entire client portfolio.

MTD ITSA quarterly updates

Cumulative year-to-date updates, 4× per tax year per business

From April 2026 onwards, sole traders and landlords above the income threshold must submit cumulative year-to-date figures to HMRC every quarter. Addlify Finance does this in one click from your Excel ledger.

The MTD ITSA calendar (TY 2025-26+)

Period	Cumulative range	Due
Q1	6 Apr → 5 Jul	7 Aug
Q2	6 Apr → 5 Oct	7 Nov
Q3	6 Apr → 5 Jan	7 Feb
Q4	6 Apr → 5 Apr	7 May

Submission flow

1Select the data range in your Excel sheet (date, category, description, amount).
2In the taskpane, choose the income source (Self-employment, UK property, Foreign property) and tax year.
3Click Build cumulative payload. The add-in rolls up income + expenses against your saved column mapping.
4Review the schema-validated payload preview.
5Click Submit to HMRC. Enter your 2FA code if prompted. The acknowledgement reference and submission timestamp are written back into Excel.

⚠️ Cumulative submissions are idempotent upserts on HMRC's side — submitting Q2 overwrites the cumulative figure HMRC has from Q1, so always send the running YTD total, never just the latest quarter's delta.

MTD VAT Returns

Boxes 1-9 submission for VAT-registered businesses

If you're VAT-registered (mandatory above the £90,000 threshold), Addlify Finance submits your standard VAT Return directly to HMRC.

Submission flow

1In the taskpane, click VAT obligations to pull open periods from HMRC.
2Pick the period you want to submit and confirm the 9-box totals derived from your sheet.
3Click Submit VAT Return. Confirm the final declaration text on screen.
4Enter your 2FA code. HMRC returns a receipt with formBundleNumber + chargeRefNumber — both written back into Excel.

ℹ️ Adjustments (e.g. partial exemption, retail scheme) go in boxes 1, 4 and 6 as separate journal lines tagged in your column mapping. Detailed examples on request — email support@addlify.uk.

Final declaration

Annual Self Assessment crystallisation after the 4th quarterly update

After Q4, you have until 31 January the following year to submit the final declaration, which crystallises your Self Assessment liability. Addlify Finance handles it from the same taskpane.

1Open the Annual summary view. The add-in pulls the calculation from HMRC.
2Review the breakdown: business profit, property income, total tax due, payments on account.
3Tick the legal declaration: "the information given is true and complete".
4Click Submit final declaration. Enter your 2FA code. Receipt + reference number written back into Excel.

⚠️ Final declaration is the most consequential action — once crystallised, amendments can only be made through HMRC's online services or by submitting a corrective return. 2FA is mandatory for this step regardless of your account settings.

Two-factor authentication

Required for HMRC submissions and account changes

To protect your fiscal data, Addlify Finance asks for a 6-digit code from your authenticator app before every HMRC submission and every sensitive account change (delete account, export data, change email, regenerate licence key).

Supported authenticator apps

Authy · Google Authenticator · Microsoft Authenticator
1Password · Bitwarden · LastPass Authenticator
Any app that supports the standard RFC 6238 TOTP protocol.

Setup (one-time, ~2 minutes)

1Open your account page and find the 🔐 Two-factor authentication card.
2Click Enable 2FA. A QR code appears.
3Scan it with your authenticator app. The app starts showing a fresh 6-digit code every 30 seconds.
4Type the current code into the confirmation field, click Verify & enable.
5Save the 10 backup codes shown. Print them or paste them into a password manager. Each is single-use, for the case where you lose your phone.

✓ After setup, every HMRC submission asks for the current 6-digit code via a small popup. Codes are short-lived (~30s) and replay-protected — once accepted, the same code can't be used again within the same 90-second window.

Lost your phone or backup codes?

Email support@addlify.uk from the address registered on your account. After verifying your identity (recent invoice, last 4 of payment card, etc.) we can:

Regenerate backup codes if you only lost the codes but still have your phone.
Disable 2FA as an emergency reset if you lost both phone and codes. You'll need to re-enable it after signing in.

OneDrive backup

Optional archive of every HMRC submission payload + receipt

Connect your personal OneDrive (Microsoft 365 / Outlook.com) to automatically archive every submission. The add-in writes a copy of the JSON payload + HMRC receipt into OneDrive/Apps/Addlify Finance/, organised by tax year and period.

Enable

1In the taskpane, click OneDrive backup → Connect. A popup signs you in with Microsoft.
2Grant Files.ReadWrite.AppFolder scope. We can only see/write inside our own app folder, never your other files.
3From now on, every successful submission auto-archives. Toggle off any time from the same panel.

ℹ️ OneDrive backup is optional and runs alongside HMRC's own copy. Useful if you ever need to prove what you filed (HMRC enquiry, accountant handover, etc.).

Account & licence

Manage your subscription, devices, billing and personal data

Your account page lives at addlify.uk/account. Sign in by clicking the magic-link sent to your registered email. From there you can:

View licence: key, plan, status, expiry, devices used.
Manage billing: open Stripe Customer Portal to change card, view invoices, cancel.
Change email: a confirmation link goes to your current address first.
Export data (GDPR): JSON dump of everything we hold on your licence.
Delete account: 30-day grace period, then permanent anonymisation. Paid commission records retained 6 years (HMRC compliance).
Rotate licence key: useful if your key leaked or you suspect device compromise.

⚠️ Every sensitive action (change email, delete, export, rotate key) asks for a 2FA code if you have 2FA enabled. Otherwise an email OTP is sent to your current address.

Data & storage

What lives on your computer, what lives on our server, what goes to HMRC

On your computer LOCAL

Data	Where	Survives reinstall?
Session-Isolated SQLite Database NEW	Secure folder (hashed per client)	Yes (persistent local store)
Column mappings	browser localStorage	Yes (per browser profile)
Recent submissions cache	browser localStorage	Yes
UI preferences (theme, locale)	browser localStorage	Yes
Excel workbook contents	your `.xlsx` file	Yes (wherever you save the file)

On Addlify servers SERVER

Data	Where	Retention
Licence key + email + plan	Hostico (UK proxy, RO data centre)	Active + 6 years post-cancellation
HMRC OAuth tokens (encrypted)	same DB	While subscription active; 18 months max per HMRC policy
API call audit log	same DB	3 years
2FA secret + backup codes (hashed)	same DB	Until you disable 2FA

At HMRC HMRC

Cumulative figures from your quarterly updates and final declarations live in your Self Assessment record at HMRC. We send the data, HMRC keeps the authoritative record. You can always view it in your Government Gateway portal.

🔒 Your Excel workbook content NEVER leaves your computer. Only the rolled-up figures (turnover, expenses, VAT box totals) are sent — and only to HMRC, not to Addlify. Our SQLite databases are isolated per client session using a secure cryptographic key derivative, guaranteeing total client-to-client privacy.

Limits & quotas

Daily HMRC API call caps per plan

Plan	HMRC API calls / day	Devices	Bulk UTR/VRN verify
Trial	20 (total over 14 days)	1	5
Solo	100	1	25
Pro	500	2	200
Cabinet	2,000	2 per seat	1,000
Enterprise	Unlimited	Unlimited	Unlimited

Submissions + reads both count as API calls. Counters reset at 00:00 UK time. If you hit the cap, top up with HMRC API credit packs (£10/100 calls, £40/500, £70/1000) from your account page. Credits do not expire.

An anti-abuse rate limit of 100 calls per hour per licence applies on top of the daily caps.

FAQ

Common questions about Addlify Finance for the UK market

How does the Session-Isolated SQLite database protect my financial data?

When you access your financial hub, the backend dynamically initializes a private SQLite database file (`.sqlite`) keyed strictly on a cryptographically secure hash of your license or session token. This ensures absolute client-to-client data isolation: other users cannot access, write, or view your records under any circumstances. It provides a zero-risk GDPR-compliant sandboxed environment.

Is Addlify Finance officially "MTD-compatible software"?

Addlify Finance uses the same HMRC public APIs that QuickBooks, Xero and FreeAgent use. We submit your quarterly updates and VAT Returns directly through these endpoints. HMRC publishes a list of recognised products — we are in the process of being listed; the underlying integration uses the production HMRC OAuth + MTD APIs either way.

What income types are supported?

Self-employment (sole trader), UK property income (rental), and foreign property income. Both cash basis and accruals basis. Final declaration covers the standard SA100 + SA103 + SA105 entries.

Does Addlify need access to my bank account?

No. We never connect to your bank. You enter or import transactions into your Excel workbook however you prefer (manual entry, CSV export from your bank, Open Banking via a separate tool). Addlify only reads the data from the sheet.

What happens if my submission fails?

The taskpane shows the HMRC error with the official error code. Common ones: BUSINESS_INCOME_PERIOD_RESTRICTION (period already submitted), RULE_INCORRECT_OR_EMPTY_BODY_SUBMITTED (mapping issue), CLIENT_OR_AGENT_NOT_AUTHORISED (re-connect HMRC). Each error has a "Fix this" link in the taskpane that explains what to do.

How do I troubleshoot HMRC connection timeouts or authorization errors?

If you see a `CLIENT_OR_AGENT_NOT_AUTHORISED` or token timeout error, verify that your Government Gateway account has MTD active. Go to the Settings tab in the taskpane, select **Disconnect HMRC** to wipe the local cache, then click **Connect to HMRC** again to authorize a fresh OAuth 2.0 token. Ensure your UTR and VRN are correct.

What is the difference between Sandbox and Production modes?

Sandbox (Test) mode allows you to execute end-to-end tax submissions completely risk-free using mock HMRC Developer endpoints. No real filings are made, and no legal liabilities are incurred. Production (Live) mode signs and files your actual tax data directly to the official HMRC system. Switch modes from the OAuth connection panel.

How do I troubleshoot OneDrive backup synchronization issues?

Microsoft Outlook/Office365 security tokens expire after 1 hour of inactivity. If your automated XML uploads to OneDrive are failing, go to Settings → OneDrive, click **Reconnect**, and approve the connection. This regenerates the secure access token locally.

Can I use the same licence on Excel desktop and web?

Yes, within your plan's device count. The licence is tied to your account, not a single Excel install. Mapping settings sync via localStorage in each browser/profile.

How does Addlify handle MTD ITSA period locking?

Once a quarterly period is submitted and crystallised, HMRC locks it. Addlify shows you the lock state in the taskpane. If you spot an error after locking, you submit a corrected next-period cumulative (which is how MTD ITSA reconciliation is designed to work) or file an amendment from your Government Gateway portal.

What about Romanian e-Factura / SAF-T?

Addlify Finance for the Romanian market is documented separately at /ro/docs-finance.html. The same licence key works for both — switch the product context in the taskpane.

I'm using HMRC sandbox / test mode. Will Addlify work?

Yes. The add-in supports both sandbox and production HMRC endpoints. During your 14-day trial we default to sandbox so you can run end-to-end submissions without affecting real records. Switch to production from the OAuth screen when you're ready.