Starting a business in the UK is mostly a paperwork problem for the first twelve months, even if nobody warns you about that part. You've got the idea sorted, maybe a few clients already, but the accounting side sits there quietly until it doesn't.
Then a VAT letter shows up, or your accountant asks for receipts you threw away in March, and suddenly it's not quiet anymore.
This checklist covers what actually needs doing in year one, roughly in the order it comes up.
Register With HMRC Before You Need To
If you're a sole trader, you need to register for Self Assessment by 5 October following the end of your first tax year of trading. Limited companies have to register for Corporation Tax within three months of starting to trade. Miss either window and HMRC can fine you even if you owe no tax yet, which catches a lot of first-time founders off guard.
Get your Unique Taxpayer Reference or company UTR sorted early too. You'll need it for almost everything else on this list, and it can take a couple of weeks to arrive by post.
Set Up Proper Record Keeping From Day One
This is the part most new business owners skip, and it's the one that causes the most pain later. Every receipt, every invoice, every bank statement - keep it, and keep it organised by month, not in a shoebox you'll sort through in January.
A simple folder structure (digital or physical) split by month, with subfolders for income and expenses, takes ten minutes to set up and saves hours at year-end. If you're not confident doing this yourself, accurate record keeping is one of those things worth handing off early rather than fixing retroactively.
Whatever method you choose, separate business and personal spending immediately. A dedicated business bank account isn't legally required for sole traders, but mixing the two makes every later step - tax returns, VAT checks, even getting a business loan - harder than it needs to be.
Know When You Need to Register for VAT
You must register for VAT once your taxable turnover passes £90,000 in any rolling 12-month period, not just your tax year. That "rolling" detail trips people up - it's not 5 April to 5 April, it's any 12 consecutive months, checked monthly.
Some businesses register voluntarily before hitting the threshold, usually because most of their clients are VAT-registered themselves and can reclaim it, or because they want to claim back VAT on big early purchases like equipment. Whether that makes sense depends entirely on your client base and margins. Getting bookkeeping and VAT set up correctly from the start means you're not retrofitting a VAT scheme onto twelve months of invoices that weren't built for it.
Sort Out Payroll Early If You're Hiring
The moment you pay anyone - including yourself, if you're running a limited company - PAYE comes into play. You'll need to register as an employer with HMRC before the first payday, set up a payroll system, and start submitting Full Payment Submissions on or before each payday.
This trips up a lot of company directors specifically. Paying yourself a salary through PAYE plus dividends is usually more tax-efficient than salary alone, but the split has to be calculated properly and reported on time. Payroll and PAYE work is one of those areas where getting the structure right in month one avoids a messy correction in month eleven.
Keep a Tax Calendar, Not Just a Filing Deadline
Most new business owners know the big one - 31 January for Self Assessment, or nine months after your company's year-end for Corporation Tax. What catches people out is everything around that date: the second Self Assessment payment on account in July, quarterly VAT returns if you're registered, payroll submissions every pay period.
Write every deadline down the day you register, not the month before it's due. A missed payment on account doesn't just cost a penalty - HMRC also charges interest from the date it was due, not the date you remembered.
Plan for Tax, Don't Just React to It
A lot of first-year business owners treat tax as something that happens to them in January, rather than something they can shape across the year. Pension contributions, the timing of equipment purchases, how profit gets extracted from a limited company - all of these affect your tax bill, but only if you act on them before the year ends, not after.
This is where tax planning earns its keep. Waiting until your accountant prepares your return to find out what you could have done differently means the opportunity's already gone for that year.
Get Your Year-End Accounts Sorted, Even If You Think You Don't Need To
Sole traders technically don't have to produce formal accounts, but trying to complete an accurate Self Assessment without them is harder than just doing the accounts properly in the first place. Limited companies have no choice - statutory accounts go to Companies House, and a separate set of figures goes into the Corporation Tax return.
Year-end isn't just a compliance exercise either. It's the point where you actually see whether the business made money once everything's accounted for, not just what the bank balance suggests. Proper accounting services and year-end accounts work gives you that picture clearly enough to make decisions with it, rather than guessing.
Don't Panic If HMRC Gets in Touch
At some point in your first few years, you might get a letter from HMRC asking questions about a return, or flagging something that doesn't quite match their records. This happens to genuinely compliant businesses too - it's not automatically a sign you've done something wrong.
What matters is responding properly and on time, with the right information, rather than ignoring it and hoping it resolves itself. If a letter like that ever lands on your desk, HMRC tax support from someone who deals with these regularly turns a stressful afternoon into a fifteen-minute phone call.
The Bigger Picture
Most of what trips up first-year businesses isn't complicated tax law - it's timing. Registering late, missing a VAT threshold check, not having records ready when a deadline hits. None of these are hard problems on their own. They're just easy to miss when you're also trying to run the actual business.
If any part of this list feels like more than you want to manage solo, business advisory support exists specifically for the stretch between "just started" and "this runs itself now." Getting it right in year one tends to make every year after it considerably less stressful.
