Resources UK tax · Registrations & thresholds

When to register for UK business taxes?

A guide on when you need to register for Self Assessment, Corporation Tax, VAT, PAYE and CIS, and what limited companies, sole traders, landlords, contractors and CIS workers should do once those obligations are triggered.

Approx. 8-9 minute read

Quick Reference: Important Registration Deadlines at a Glance

  • Self Assessment:

    You must register if your trading or property income is above £1,000 in a tax year (or if you want to claim expenses).
    🕮 Register by 5 October after the end of the tax year.
    🕮 File your return and pay any tax by 31 January.

  • Corporation Tax:

    You must register your company with HMRC within 3 months of starting any business activity.
    🕮 File your CT600 within 12 months of the company year end.
    🕮 Pay Corporation Tax 9 months and 1 day after year end.

  • VAT:

    You must register as soon as your VATable income exceeds the VAT threshold of £90,000 in any rolling 12 month period, or if you know you will exceed it in the next 30 days.
    🕮 VAT returns and payments are due 1 month and 7 days after the VAT period ends.

  • PAYE:

    You must register before the first payday.
    🕮 Report pay to HMRC (RTI) on or before each payday.
    🕮 Pay PAYE/NIC by the 22nd of the following month if paying electronically.

  • CIS:

    You must register before you start working as a subcontractor, and register as a contractor before you first pay subcontractors.
    🕮 Monthly CIS returns are due by the 19th of the following month,
    🕮 with payments due by shortly afterwards by the 22nd.

  • Auto-enrolment:

    You must check your pension duties as soon as you take on staff.
    🕮 Submit your declaration of compliance within 5 months of your duties start date.

1. The main UK taxes small businesses deal with

Getting the tax registrations right is just as important as keeping good bookkeeping records. Register too late and HMRC can charge penalties and interest, even if your accounts are tidy. Register too early or on the wrong basis and you may add unnecessary admin for little benefit.

Most small businesses and landlords will run into some or all of the following:

  • Self Assessment: personal tax returns for sole traders, partners, landlords and many company directors.
  • Corporation Tax: for limited companies, normally reported on the company's CT600 return.
  • VAT: when VATable turnover exceeds the registration threshold, or sometimes voluntarily below it.
  • PAYE / payroll: when you pay employees or directors through payroll.
  • CIS (Construction Industry Scheme): for construction contractors paying subcontractors, and subcontractors having CIS deducted from their income.
  • Auto-enrolment pensions: employer duties once staff meet age and earnings triggers.

The next sections look at each area in turn, with clear triggers and dates for the main business types we work with.

2. When to register for Self Assessment

Self Assessment is the system used to report personal income that is not fully dealt with under PAYE. That includes trading profits, rental income, many types of investment income and dividends from your own company.

Sole traders and side businesses

You normally need to register for Self Assessment if your gross self-employed income in a tax year is:

  • over the £1,000 trading allowance; or
  • below £1,000 but you choose to register so you can claim actual expenses or losses.

It does not matter whether this is your main income or a side business alongside a job.

Registration deadline:

if you first need to complete a tax return for a particular tax year, you should usually register with HMRC by 5 October following the end of that tax year.

Return and payment deadlines:

  • Online tax return due by 31 January after the tax year.
  • Any balancing tax and first payment on account (if due) also by that 31 January.
  • Second payment on account, if due, by 31 July.

Examples: sole traders

  • Example 1: You begin offering beauty treatments from home in October and earn £3,000 before 5 April. You should register for Self Assessment by 5 October, with your return and tax due the next 31 January.
  • Example 2: You sell items online occasionally and make £600 in the year. You are under the trading allowance. You usually do not need to register unless HMRC ask you to, or you want to declare a loss or claim higher actual expenses.

Landlords and property income

Property income has its own £1,000 property allowance. In broad terms, you need Self Assessment if:

  • your gross rental income from residential or commercial property exceeds £1,000; or
  • your gross rental income is under £1,000 but you want to claim actual expenses, including mortgage interest on qualifying residential lets, repairs, insurance, service charges and agents' fees.

For jointly owned property it is common for each owner to report their own share of income and costs. More bespoke arrangements (for example, married couples changing the split of income) should be checked with an accountant.

The same 5 October registration deadline and 31 January filing / payment deadlines apply as for sole traders.

2.3 Partners and company directors

Partners in a partnership generally need Self Assessment to report their share of partnership profits, even if the partnership itself also files a separate return.

Company directors are not automatically required to file Self Assessment returns, but many do because they receive:

  • dividends from their own company;
  • benefits in kind (for example, private medical insurance); or
  • other income that is not fully dealt with through PAYE.

In practice, if you are a director of a small limited company taking a mixture of salary and dividends, you should expect to be in Self Assessment and plan for it from the beginning, using the same 5 October and 31 January timeframes.

3. When a limited company must register for Corporation Tax

Forming a company at Companies House does not automatically complete all of the tax registrations. As soon as a company becomes active (e.g. it starts trading, buying stock, incurring advertising costs, employing staff or earning interest) it falls within the Corporation Tax regime.

You normally need to tell HMRC that the company is active and register for Corporation Tax within 3 months of starting business activity.

Once registered, HMRC will set up your company's Corporation Tax record and expect:

  • a company tax return (CT600) within 12 months of the end of the accounting period; and
  • payment of Corporation Tax usually within 9 months and 1 day after the year end for small companies.

Bookkeeping implications for companies

From the date the company starts trading, all income and costs should be recorded in the company’s records, not in the director’s personal accounts. Using personal bank cards or accounts without recording things properly can cause delays and extra work when the first accounts and CT600 are prepared.

4. When to register for VAT

VAT registration is driven by taxable turnover, not profit. The main compulsory trigger is when your VATable turnover in a rolling 12 month period goes over the registration threshold. At the time of writing this is £90,000, but you should always check the current HMRC figure.

In broad terms, you must register for VAT if:

  • at the end of any month your VATable turnover for the past 12 months is over the threshold; or
  • you expect to go over the threshold in the next 30 days alone (for example, a large contract starts).

Once registered, most small businesses submit VAT returns quarterly. The filing and payment deadline is normally 1 calendar month and 7 days after the end of the VAT period.

Who needs to watch the VAT threshold closely?

  • Consultants and contractors: especially where day rates increase or where you take on several contracts in a short period.
  • Commercial landlords: where you have opted to tax a property or charge VAT on rent and service charges.
  • Residential landlords: residential rent is normally exempt from VAT, but businesses with a mix of residential and commercial property, or serviced accommodation, still need clear records so VATable income can be tracked correctly.
  • CIS subcontractors and locums: whose turnover creeps up over several contracts and can easily pass the threshold mid year.

Some businesses choose to register voluntarily below the threshold (e.g. if most of their customers are VAT registered and can reclaim VAT, or where input VAT on costs is significant). Voluntary registration still brings full VAT obligations and deadlines, so it should be considered alongside cash flow and admin capacity.

5. When to register for PAYE as an employer

If you pay staff or directors, you may need to operate PAYE even where their pay is relatively modest. Payroll is about reporting and National Insurance as well as income tax.

In general, you must register as an employer and operate PAYE if any employee or director:

  • earns at or above the weekly National Insurance lower earnings limit; or
  • receives benefits, expenses, a pension or has another job.

Key PAYE timing points:

  • Register as an employer before the first payday.
  • Submit payroll reports to HMRC on or before payday using Real Time Information (RTI).
  • Pay PAYE and National Insurance to HMRC, usually by the 22nd of the following tax month when paying electronically.

Examples in practice

  • Single-director company: a limited company paying its sole director a regular monthly salary should almost always have a PAYE scheme.
  • Small café or shop: as soon as part-time staff are close to or above the NIC thresholds, or have other jobs, a PAYE scheme is usually required.

6. CIS: contractors and subcontractors

In the construction industry, the Construction Industry Scheme (CIS) sits on top of normal tax rules. It affects how tax is deducted when contractors pay subcontractors.

When to register as a CIS subcontractor

You are normally treated as a CIS subcontractor if:

  • you work in construction for a contractor; and
  • you are paid under deduction rather than as an employee on PAYE.

It is usually worth registering with HMRC as a subcontractor so that:

  • contractors can verify you and deduct CIS tax at the correct rate; and
  • you can reclaim CIS deductions through your company's CT600 or your own Self Assessment return.

In practice, subcontractors should register before or as soon as they start working under CIS, not months later when the first tax return is due.

When to register as a CIS contractor

You may need to register as a CIS contractor if you:

  • pay other self-employed workers or companies to do construction work for you; and
  • are not simply paying wages under PAYE.

CIS timing rules in outline:

  • Register as a contractor before you first pay a subcontractor under CIS.
  • Verify each subcontractor with HMRC before making the first payment.
  • File CIS returns by around the 19th of the following month and pay CIS deductions to HMRC shortly afterwards (often by the 22nd if paying electronically).

7. Auto-enrolment pension duties

Employers in the UK must consider workplace pension duties as soon as they take on staff. Depending on age and earnings, workers may need to be automatically enrolled in a qualifying pension scheme.

For many small employers the practical steps are:

  • find your duties start date - usually when you first employ someone;
  • assess staff each pay period to see who needs to be enrolled or given information; and
  • submit a declaration of compliance to The Pensions Regulator.

The declaration of compliance is normally due within 5 months of your duties start date. Even where there is only a director and no other staff, it is still important to check the rules and keep evidence that you have considered them.

8. Making Tax Digital and digital record keeping

Making Tax Digital (MTD) is the gradual move towards mandatory digital records and electronic filing through software. At the time of writing:

  • most VAT registered businesses above the VAT threshold must keep digital records and file VAT returns using compatible software; and
  • further MTD rules for landlords and sole traders are planned, but detailed dates and requirements are still evolving.

In practical terms, using reliable bookkeeping software from an early stage makes it easier to comply with MTD, handle VAT and generate accurate figures for Self Assessment and Corporation Tax.

How Greater London Bookkeepers can help?

At Greater London Bookkeepers, we take the pressure of tax registrations, bookkeeping structure and HMRC compliance off your shoulders. Instead of you having to keep track of rules, thresholds and deadlines, we set everything up correctly and keep it running smoothly in the background.

We handle the practical work that most business owners do not have the time or the desire to manage. That includes the HMRC registrations you need, clean bookkeeping records, accurate VAT, payroll and CIS reporting, and clear monthly information you can rely on. Our goal is simple: no stress, no surprises, no last minute scrambles.

  • We register you for the correct taxes and fix missing or incorrect HMRC setups.
  • We maintain tidy, accurate bookkeeping so deadlines and returns are handled on time.
  • We monitor VAT, payroll, CIS and income thresholds so problems are prevented early.
  • We prepare the records your accountant needs, reducing delays and extra fees.

Many UK businesses struggle not with the bookkeeping itself, but with the constant flow of VAT, payroll, CIS and tax administration that sits behind it. Our role is to take ownership of that process. We monitor thresholds, handle registrations, maintain tidy records and prepare the information your accountant will need for year end and tax returns.

If you would like us to review your current bookkeeping setup or take over the compliance tasks that are currently taking up your time, you can outline your situation on our contact page.

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