CT41G letter from HMRC: what it is and what to do next

In short: A CT41G is the letter HMRC sends a newly incorporated company to give it its 10-digit Unique Taxpayer Reference (UTR). HMRC's system issues it automatically the day after the company's Corporation Tax record is set up (HMRC manual COM40070). Keep it, then tell HMRC within 3 months of the company starting to do business. Taxley prepares and files the Company Tax Return (CT600) for £44.50 (promotion price until 31 Dec 2026; £89.00 from 1 Jan 2027) with micro-entity accounts, then files the accounts at Companies House once the return is paid and finished.

Take the 30-second check to see whether Taxley fits your company, or read what a UTR is and where to find it.

Key facts (checked on 1 October 2026)

What is a CT41G letter from HMRC?

A CT41G is HMRC's first Corporation Tax letter to a new company. HMRC's manual lists it as the "Corporation Tax information for new companies" form and says HMRC's system issues it automatically the day after the company's Corporation Tax record is set up, which happens when Companies House accepts the incorporation (HMRC manual COM40070).

The letter matters because it carries the company's Unique Taxpayer Reference. HMRC's manual says that until the CT41G is issued, the company doesn't know its UTR and can't contact HMRC or register for HMRC's online services (HMRC manual COM40070). A few new records need a manual check first, for example when the company name or registered office address is too long or contains characters HMRC's system can't hold, and HMRC then issues the form by hand. The letter goes to the registered office: GOV.UK asks you to check that address before setting the company up for Corporation Tax, because it is where all letters are sent (GOV.UK: Add Corporation Tax services to your business tax account). The CT41G isn't a tax bill. Nor is it the notice that makes a Company Tax Return (CT600) compulsory; that is a separate form, the CT603.

What is on a CT41G, and what is the UTR for?

The key item on it is the company's 10-digit UTR. The CT41G also explains that a company which couldn't give HMRC its start-up details when it registered can supply them online (HMRC manual COM40030). You need the UTR to add Corporation Tax to the company's HMRC account, to tell HMRC the company is dormant and to file every CT600.

The start-up details HMRC wants are set by law. They include the date the company's first accounting period began, its name and registration number, its principal place of business, the date to which it intends to make up accounts, and details of any business it took over or any parent company (HMRC manual COM40030). Keep the UTR apart from two other numbers. The company registration number (CRN) comes from Companies House. The 17-character Corporation Tax payment reference, which changes each accounting period, appears on HMRC's notice to deliver a return and its reminders (GOV.UK: Pay your Corporation Tax bill). If the CT41G hasn't arrived 15 working days after the company was registered, GOV.UK says you can request the UTR online (GOV.UK: Add Corporation Tax services). Our guide on what a UTR is and where to find it covers the other places to look.

What should you do after receiving a CT41G?

Keep the letter with the company's records, then answer one question: has the company started to do business? If it has, add Corporation Tax to its HMRC business tax account within 3 months of starting. If it hasn't, it is usually dormant for Corporation Tax, with nothing to file unless HMRC asks (HMRC: Corporation Tax trading and non-trading).

What to do after a CT41G arrives

What counts as doing business decides which row applies. GOV.UK says to add Corporation Tax when the company starts to do business, which includes buying, selling, advertising, renting a property and employing someone (GOV.UK: Add Corporation Tax services). HMRC's guidance also treats providing services, earning interest, managing investments and receiving any other income as active. Preparation doesn't count: HMRC gives writing a business plan, negotiating contracts and spending money to decide whether to start a business as examples of activities that aren't trading (HMRC: Corporation Tax trading and non-trading). Being dormant for Corporation Tax doesn't excuse the company from Companies House, where it still files annual accounts and a confirmation statement (GOV.UK: Dormant for Companies House).

How do you tell HMRC your company has started trading?

Add Corporation Tax services to the company's business tax account. Sign in with the company's Government Gateway user ID, select "Services you can add", then "Enrol for service" for Corporation Tax. You'll need its registration number, the date it started to do business, the date its first accounts are made up to, and its UTR (GOV.UK: Add Corporation Tax services).

The start date you give matters, because GOV.UK says the company's first accounting period starts from it. HMRC then posts a Corporation Tax activation code to the registered office within 10 days, or 21 days if you live abroad, with instructions for activating the service and the deadline for paying Corporation Tax (GOV.UK: Add Corporation Tax services). Our Corporation Tax activation code guide covers what to do if the code doesn't arrive.

The 3-month limit comes from the law: a company must tell HMRC in writing when its first accounting period began, no later than 3 months after it began (Finance Act 2004 s.55). HMRC also accepts the details in a letter signed by a director or the company secretary (HMRC: Corporation Tax trading and non-trading). A second rule covers a company HMRC hasn't yet asked for a return: if it is chargeable to tax for an accounting period and hasn't received a notice to deliver, it must tell HMRC within 12 months of the end of that period (FA 1998 Sch 18 para 2).

What if the company hasn't started trading yet?

Then it is usually dormant for Corporation Tax. GOV.UK lists a new limited company that hasn't started trading as dormant, and says a company can be dormant between incorporation and starting to trade. There's usually no Company Tax Return for that time unless HMRC sends a notice to deliver one (GOV.UK: Dormant for Corporation Tax).

When you add Corporation Tax later decides whether the dormant months need a return. GOV.UK says that if you add Corporation Tax services before the company's accounting reference date, you usually don't file a return for the dormant period. If you add them after that date, you must file two returns, one for the dormant period and one for the trading period (GOV.UK: Your limited company's first accounts and Company Tax Return). Check the first notice to deliver as well: if it covers both the dormant and the trading period, GOV.UK says two returns are needed. A company that won't trade at all can tell HMRC online that it is dormant, using its UTR. After that it files no Company Tax Return unless HMRC asks for one or it starts trading (GOV.UK: Tell HMRC your company is dormant). Our dormant company tax return guide explains what to file if HMRC does ask.

When do a new company's first accounting period and deadlines fall?

The first accounting period starts when the company starts to do business, not when the CT41G arrives, and lasts at most 12 months. Tax is due 9 months and 1 day after it ends, the CT600 12 months after (GOV.UK: Company Tax Returns). First accounts over 12 months are due within 21 months of incorporation (Companies House: first accounts).

Worked timeline (an illustration using HMRC's and Companies House's rules): a company is incorporated on 15 September 2026. It starts trading on 1 November 2026 and adds Corporation Tax services the same month. Its accounting reference date is 30 September 2027.

In this example the company prepares one set of accounts, for 15 September 2026 to 30 September 2027, and files one CT600, for 1 November 2026 to 30 September 2027. There's no return for the dormant weeks, because it added Corporation Tax before its accounting reference date (GOV.UK: first accounts and Company Tax Return). The accounts cover more than 12 months, so Companies House allows 21 months from incorporation, or 3 months from the accounting reference date if that is later (Companies House: deadlines for first accounts). An accounting period begins when a company comes within the charge to Corporation Tax, which for a UK company is when it starts to carry on business (CTA 2009 s.9).

Had the company started trading on 15 September 2026, its first accounts would span two accounting periods: 15 September 2026 to 14 September 2027, and 15 to 30 September 2027. Corporation Tax would be due on 15 June 2028 and 1 July 2028. Both returns would be due on 30 September 2028, because the filing date runs to 12 months after the end of the period of account when that period is 18 months or shorter (FA 1998 Sch 18 para 14). Our guide to first company accounts and two CT600s explains the split.

How is a CT41G different from a CT603 notice to deliver?

The CT41G only introduces the company and its UTR. The CT603, the "notice to deliver a Company Tax Return", is what makes a return compulsory. HMRC issues one about a month after each accounting period ends, and the company must then file even with a loss or no Corporation Tax to pay (GOV.UK: Company Tax Returns).

The HMRC letters a new company receives

HMRC's manual explains that each notice to deliver names a period of no more than 12 months, ending on the same date as an accounting period on HMRC's record, and shows the period for which returns are required (HMRC manual COM130130). The same page says HMRC sends a combined CT208 payment and return reminder 42 days before the filing date if it has received neither, and that agents don't receive copies of notices to deliver. The CT603 also carries the 17-character payment reference for that accounting period (GOV.UK: Pay your Corporation Tax bill). If a notice arrives late, the return isn't due until at least 3 months after the notice was served (FA 1998 Sch 18 para 14).

Can Taxley file your company's first CT600 after the CT41G?

Yes. Taxley (taxley.co.uk), UK online software that prepares and files the Company Tax Return (CT600) with HMRC and the annual accounts with Companies House, files a company's first CT600 as well as later ones. It also splits a first period longer than 12 months into two returns.

Taxley files the return with the company's own Government Gateway user ID, the login you add Corporation Tax to with the activation code, so set that up first. It charges one fee per return: £44.50 (promotion price until 31 Dec 2026; £89.00 from 1 Jan 2027) with micro-entity accounts, £84.50 (promotion price until 31 Dec 2026; £169.00 from 1 Jan 2027) with small-company accounts or £9.50 (promotion price until 31 Dec 2026; £19.00 from 1 Jan 2027) for a dormant return. The fee includes filing the accounts at Companies House once the return is paid and finished, using the company's 6-character Companies House authentication code. Adding Corporation Tax to the company's HMRC account happens on HMRC's own service, and Taxley doesn't file the confirmation statement. Take the 30-second check to see whether Taxley fits your company, or start your return.

Frequently asked questions

Is a CT41G a tax bill or a demand to file a return?

No. The CT41G gives a new company its UTR and explains how to send HMRC any start-up details it couldn't give at registration. A return becomes compulsory only when HMRC sends a notice to deliver, form CT603, about a month after an accounting period ends (HMRC manual COM130130).

What if my CT41G never arrived?

GOV.UK says that if you haven't received the company's UTR 15 working days after registering it, you can request it online. Check the registered office address at Companies House first, because HMRC sends its letters there (GOV.UK: Add Corporation Tax services).

When will HMRC confirm my company's accounting period dates?

After you add Corporation Tax services. GOV.UK says HMRC then sends a letter giving the dates of your accounting period. You can also check them in the company's business tax account, and tell HMRC if you think they're wrong (GOV.UK: Accounting periods for Corporation Tax).

Can I add Corporation Tax using my personal Government Gateway account?

No. GOV.UK says you create a Government Gateway user ID and password for the company when you register it, and that you can't use your personal Government Gateway ID for this (GOV.UK: Register your company). Use the company's own login.

Does a dormant company receive a notice to deliver a return?

Not normally. HMRC's manual says a notice to deliver isn't issued to a dormant company (HMRC manual COM130130). If one arrives anyway, the company must file a return showing it was dormant. Once HMRC knows it is dormant, it files no further return unless asked.

General information, not personalised tax or accounting advice.