SmartScanit MTD — sandbox harness

Prototype. Points at the HMRC sandbox. Not for production data.

🌍 LanguageSense™your tax, explained in your own language
ℹ️ Important — what this software supports

This software supports self-employment income only — it does not support property income. If you need to report UK or foreign property income under Making Tax Digital, please use software that supports property income.

This release covers in-year digital records, quarterly updates and in-year tax estimates. The End of Year (Final Declaration) journey is not yet available — we are building the product in stages and it will follow in a later release. If you need to finalise your tax year, please use software that supports the final declaration.

Find software that's compatible with Making Tax Digital for Income Tax on GOV.UK →

0 · Create a sandbox test user

Generates a fake individual (Government Gateway login + NINO) to log in with at step 1. Do this once and keep the details.

1 · Connect to HMRC with your own Government Gateway

You log in with your own Government Gateway account and give this software permission to send YOUR figures to HMRC. Nobody files for you — you review and submit your own quarterly updates. The callback shows the access token — copy it into steps 2 and 3.

Connect to HMRC →
2 · Check your quarterly obligations

See which quarterly update periods HMRC is expecting from you, and which are still open.

3a · Keep your digital records

Add each income and expense item as it happens. These are your digital records for Making Tax Digital — your quarterly update in step 3b is worked out from them automatically. To change a figure, edit the record here; figures cannot be typed straight into the submission.

3b · Review and submit your own quarterly update

Check your cumulative (year-to-date) figures below, then submit your own quarterly update to HMRC. Figures are totals so far this tax year, not just this quarter.

Your cumulative figures (from your records)
These figures are worked out from your digital records for the period above. To change them, edit the records in step 3a — they cannot be typed here.
Finds your Business ID and income sources held by HMRC.

Shows the accounting period, accounting type and address HMRC holds for the Business ID above.

Retrieves the cumulative in-year summary HMRC currently holds for this business and tax year.

You are submitting your own figures to HMRC (sandbox). Review them first — you stay in control.

4 · Work out your tax

Ask HMRC to calculate your tax from the figures you have submitted, then view the result. During the year, use the normal in-year calculation; tick the box below when you are ready to finalise your year.

This calculation is only based on information HMRC have received about your income and expenses to . This may change as we receive further information about you during the tax year.

5 · Final declaration

This is your legal declaration to HMRC that the information you have given is correct and complete to the best of your knowledge. You submit it yourself — check your calculation in step 4 first.

⚠ This is the binding year-end step. Once submitted, your tax year is finalised (crystallised). Only submit when you are sure.

Not part of this release: the final declaration is not yet available in this stage of the software — this card is for sandbox testing by SmartScanit staff only. See the note at the top for software that supports the final declaration.

🛠 Developer check · fraud-prevention headers

For SmartScanit staff: checks that the technical headers this software must send to HMRC by law are complete and accurate. Clients don't need this step.

Privacy & what we send to HMRC · Support · Terms