Our services · Watford, Bushey & North West London
Your Self Assessment filed accurately, on time and optimised for every allowance you are entitled to. No January panic.
The Self Assessment deadline is 31 January following the end of the tax year, for both filing online and paying any tax owed. Missing it triggers an automatic £100 penalty even if you owe nothing. Paper returns are due earlier, by 31 October.
Whether it is your first return or your fifteenth, Self Assessment has a habit of eating evenings and creating stress you do not need. We prepare and file returns for company directors, sole traders, landlords and higher earners across Watford, Bushey and North West London, and we do it properly: every allowance claimed, every figure checked, filed well before the deadline.
We do not just type your numbers into a form. We look at the whole position. Payments on account, pension relief, Gift Aid, the Marriage Allowance, expenses you did not know you could claim. The difference between a filed return and a well prepared one is usually money.
| Tax year | 6 April to 5 April |
| Online filing and payment deadline | 31 January |
| Paper return deadline | 31 October |
| Second payment on account | 31 July |
| Late filing, immediate | £100 |
| 3 months late | £10 per day, up to £900 |
| 6 months late | 5% of tax due or £300, whichever is greater |
| 12 months late | A further 5% or £300 |
| Personal allowance | £12,570 |
| Personal allowance taper | Reduces above £100,000, gone at £125,140 |
| Trading allowance | £1,000 |
| Property allowance | £1,000 |
| Marriage Allowance | Up to £252 per year |
Filing in May does not mean paying in May. The payment deadline stays 31 January regardless of when you file. What early filing buys you is eight months of knowing exactly what you owe, which is the difference between planning for a bill and being ambushed by one.
It also means any refund arrives sooner, and if your income has fallen there is time to reduce your July payment on account properly rather than in a rush.
31 January following the end of the tax year for online filing and for paying any tax due. For the 2025/26 tax year that means 31 January 2027. Paper returns must be filed by 31 October. The £100 late filing penalty applies automatically even if your tax bill is nil.
Common triggers include self-employment income over £1,000, rental income, untaxed income such as dividends above the allowance, income over £150,000, capital gains above the annual exempt amount, or being a company director with untaxed income. If you are unsure, ask and we will tell you straight rather than filing unnecessarily.
Advance payments toward next year's bill, due 31 January and 31 July, each normally half of the previous year's liability. They are required if your bill exceeded £1,000 and less than 80% was collected at source. They can be reduced where your income has genuinely fallen, though reducing them wrongly triggers interest.
£100 immediately, then £10 a day from three months up to £900, then 5% of the tax due or £300 at six months, and the same again at twelve months. Interest also runs on unpaid tax. The penalties are separate from the tax itself and are not reduced by having a small bill.
Costs incurred wholly and exclusively for the business: materials, subcontractors, business travel, professional fees, insurance, and a proportion of home and phone costs where you work from home. The mistakes we correct most often are people missing home-working costs, or claiming for things HMRC will disallow on inspection.
Because the personal allowance tapers by £1 for every £2 of income above £100,000, disappearing entirely at £125,140. That creates an effective 60% marginal rate on that band. Pension contributions and timing of income can reclaim a significant part of it, which is one of the most common planning conversations we have.
We provide self assessment tax returns across Watford, Bushey, Harrow and North West London. Related services: Bookkeeping and Making Tax Digital · VAT Returns and Registration · Payroll and PAYE · Corporation Tax · Company Accounts · CIS for Construction.
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