Getting set up to file your own Corporation Tax

What does 'getting set up' actually mean?

Filing your first Corporation Tax return feels like a wall when you have not done it before. The good news is that the wall is really a short list of admin jobs, and most of them are one-off. Do them once, in order, and you are set up for good.

Setting up your company at Companies House is a separate thing, and you have probably already done it (that is what gave you your company registration number). This guide is about the HMRC and filing side: the references, sign-ins and codes you need before a single figure can go anywhere.

A few of these jobs are yours to do directly with HMRC and Companies House. We cannot do them for you, because they are tied to your company's identity and post to your registered office. We will be straight about which is which as we go. Once they are done, the hard part, the figures and the filing, is the part we take off your hands.

Step 1: Tell HMRC your company is active

When your company starts doing business, you have to tell HMRC it is active. 'Doing business' means trading: selling, buying to sell, providing a service, earning interest, or otherwise bringing money in to make a profit.

There is a clock on this. You must tell HMRC within 3 months of starting to trade. The day you started doing business is the day the 3-month clock begins. There is nothing to gain by leaving it, so the simplest move is to do it as soon as you have started.

You do this online through your company's business tax account, and HMRC then treats your company as active for Corporation Tax. This is a step you do directly with HMRC. It is free and quick, and we do not do it for you. If your company has not started trading at all yet, you tell HMRC it is dormant instead, and the 3-month clock only starts when you begin.

Step 2: Have your UTR (your company's tax reference)

Your UTR is a 10-digit number HMRC uses to recognise your company for Corporation Tax. Think of it as your company's tax membership number. Every time your company deals with HMRC about Corporation Tax, the UTR is how they pull up the right file.

You do not apply for it. HMRC creates it once your company is set up, and posts the number to your company's registered office, the official address you gave Companies House. The letter usually arrives within a couple of weeks of the company being set up.

• It is 10 digits long, and it belongs to your company and no one else's.
• It is posted to your registered office, so keep an eye on the post going to that address.
• It is not the same as your Companies House registration number, and not the same as your own personal tax number.

If the letter has not turned up within about 15 working days of setting the company up, or you have mislaid it, you can ask HMRC for it online. You need the UTR to register for, sign in to and file your Corporation Tax, so it is one of the first things to have ready.

Step 3: Set up your HMRC online account (Government Gateway)

To deal with HMRC online, your company needs a business tax account, and to sign in to it you use a Government Gateway user ID and password. The Government Gateway is simply HMRC's sign-in system, the same front door used for most online tax services.

If you do not have a Government Gateway user ID yet, you create one as part of signing in for the first time. You will end up with two things to keep safe: a user ID (a string of digits HMRC gives you) and a password you choose. Write them down somewhere you will find them again, because you will need them every year.

Once you are signed in, you add the Corporation Tax service to that account using your UTR. That links your company's tax record to your sign-in. This is the account through which the return is sent and the tax is paid, whether you do that yourself or we do it on your behalf.

Step 4: Get your Companies House authentication code

Here is the part new directors most often miss, because it is a different organisation. Your accounts go to Companies House as well as to HMRC, and to file anything with Companies House online you need its authentication code.

The authentication code is a 6-character code, a mix of letters and numbers, that Companies House posts to your company's registered office. It is like an online signature for your company: it proves a filing is genuinely from you. You request it through Companies House online, and like the UTR letter, it arrives by post to your registered office, so allow a few days for it to come.

Keep this code with your UTR and Government Gateway details. It is yours to request from Companies House, not something we can get for you, and you will need it before your accounts can be filed there.

Step 5: Know your key dates

Once the references and codes are sorted, the last piece is knowing your dates. Corporation Tax has a quirk that catches people out: the date you pay and the date you file are not the same, and your accounts have their own deadline at Companies House.

The three dates that matter

• Your accounting period, usually your company's financial year. The end of it is your 'year end', and most of your deadlines count from that day.
• Pay your Corporation Tax 9 months and 1 day after your year end. This is the one people are surprised by: you pay before you file.
• File your Company Tax Return (the CT600) with HMRC within 12 months of your year end.
• File a copy of your accounts with Companies House within 9 months of your year end.

Missing a deadline means a penalty, and the Companies House one for late accounts starts the moment you are even a day over. The safe approach is to not file at the last minute and to use something that tracks both deadlines for you.

Step 6: Then you can file (this is the part we do)

With your company active, your UTR in hand, your Government Gateway sign-in ready, your Companies House code to hand and your dates known, you are set up. Now comes the bit you do not have to learn.

With SimpleReturns, you connect your bank or upload a statement. We build your accounts, work out the tax, put everything into the format HMRC needs, and show you every figure in plain English before anything is sent. You check it, you approve it, and we file your return to HMRC and your accounts to Companies House.

It is £99, once, no subscription. The references and codes above are yours to gather once. The yearly figures and the filing are the parts we take care of, so you never have to work out the tax yourself.

Your quick checklist

Tick these off before your first filing:

• Told HMRC your company is active, within 3 months of starting to trade (or told them it is dormant if it has not started).
• Got your 10-digit UTR, posted to your registered office (ask HMRC online if it has not arrived).
• Set up a Government Gateway user ID and password, and added the Corporation Tax service using your UTR.
• Requested your 6-character Companies House authentication code, posted to your registered office.
• Worked out your year end, and noted the dates: pay tax 9 months and 1 day after, file the return within 12 months, accounts to Companies House within 9 months.
• Got your bank statements or a way to connect your bank, ready for us to do the figures.

The first four are one-off jobs you do directly with HMRC and Companies House. Once they are done, they are done for good, and the rest is ours.