How to Onboard Your Clients on FileThat: A Step-by-Step Guide for Accountants

Before You Start

You need a FileThat account set up as an agent, with your Agent Reference Number (ARN) from your HMRC agent services account. When you connect FileThat to HMRC, choose Agent Services, Self Assessment and VAT; one sign-in can cover all three.

Agent Services is what lets you send authorisation requests and check them. Self Assessment is what FileThat uses to fetch your clients' businesses, and Self Assessment and VAT are what it files with. Once a client has authorised you, you act for them through those connections, the same kind an individual makes for themselves. Your clients do not connect FileThat to HMRC.

For each client you need their name and email address, and a National Insurance number, a VAT number, or both. To ask HMRC for authorisation you also need the postcode HMRC holds for an Income Tax client, or the VAT registration date for a VAT client. You can add those later, but the request cannot be sent without them.

Step 1: Upload Your Client List

Open the Client Portal and choose Upload client list. Download the template, fill in one row per client, and upload it as CSV or Excel. A file holds up to 100 clients; if you have more, upload them in further files.

If you know what a client does, add a business type: Self-employment, UK property, Foreign property or VAT only. Their business is then created at upload, ready to take HMRC's details later. If you leave it blank, their businesses are created from what HMRC lists for them in step 4.

Good rows are saved and bad rows are reported, with the row number and the reason, so one mistake does not stop the rest. An email address that already has a FileThat account is a failed row. You can download the failed rows, fix them and upload them again.

The upload writes only to FileThat. Nothing is sent to HMRC and no email is sent to your clients at this stage.

Step 2: Ask Each Client for Authorisation

Each uploaded client now has a card headed "Setting up", with a Next line and one main button. For a client who has not authorised you with HMRC yet, the next step is Request Income Tax authorisation or Request VAT authorisation, on their own card.

FileThat sends the request to HMRC with the details from your upload. If HMRC accepts it, the card reads "Waiting for the client to accept". Press Check requests with HMRC and the card offers the client's link. Copy it and send it to your client: they sign in to HMRC with their own Government Gateway details and accept.

With a long list, there is a quicker way to find out who needs asking. Press Set up businesses for your clients first: HMRC answers for each one, and those who have not authorised you are marked "Not authorised yet". Request authorisation then sends a request for each of them in one go, one at a time.

If a client has already authorised you through HMRC, the request tells you so and the card moves straight to "Authorised". Nothing needs sending.

Step 3: Check Your Requests

When clients have accepted, press Check requests with HMRC. It asks HMRC once about every request you have sent and moves each client on: accepted requests become "Authorised", and declined or expired ones say so, ready for you to send again.

FileThat never calls HMRC in the background on this page. Each step happens when you press its button, so you always know what was asked and when.

Step 4: Set Up Their Businesses

For an authorised client, the next step is Set up businesses. FileThat asks HMRC for the client's businesses and creates each one with its type and its HMRC business ID. If you gave a business type at upload, HMRC's details are attached to that business; it is not created a second time.

A VAT number sits on exactly one business: the client's self-employment if they have one, otherwise a VAT-only business of its own. VAT reads "Set up" once HMRC has confirmed your VAT authorisation for that client.

Set up businesses for several clients at once with the button at the top of the list. HMRC limits how quickly client data can be requested, so clients are set up one at a time. Keep the page open until it finishes.

Step 5: Invite Your Client

When everything else on the card is done, the Next line tells you that you can now invite your client to start creating their records, with an Invite button beside it. Press it and your client is emailed their FileThat login.

This is deliberately the last step, and it is yours to take. A client who is asked to log in before their business exists finds nothing they can do, and the first thing they do is ring you. Inviting them last means they arrive at an account that is ready.

Once a client is invited, their setting-up card goes and their businesses appear as cards in your client list, where you see their obligations and file for them.

When Something Needs Fixing

If HMRC refuses a request, the card shows HMRC's own message and its code, and the client appears under Needs attention. The usual cause is a postcode or VAT registration date that does not match HMRC's record. Choose Edit details, correct it and send the request again.

A National Insurance or VAT number cannot be changed while HMRC holds a request for it. Use Cancel request first, which withdraws the request at HMRC, then correct the number.

A client's email, name and mobile can be corrected until they first log in. After that the account is theirs and they change those details themselves. If an invitation email fails to send, the card says so and the same Invite button sends it again.

If HMRC lists no businesses for a client and you gave no business type, the card tells you there is nothing to invite them to yet, and offers Set up organisation so you can create their business yourself.

What Your Client Sees

Your client logs in to their own FileThat account and keeps their digital records there: sales, expenses, receipts and mileage. They do not see HMRC filing screens, and they do not connect to HMRC.

You review their records from your Client Portal, flag anything that needs correcting, and file their quarterly updates, VAT returns and final declaration on their behalf. Read more about how FileThat works for accountants.