Selling a rental property, gifting a second home to family or disposing of business shares can create a tax bill well before your usual annual accounts are due. The capital gains deadline is not one date that applies to every sale. It depends on what you have sold, when the disposal took place and whether you are required to complete a Self Assessment tax return.
For business owners, landlords and private clients, getting this wrong can mean interest and penalties at a point when the sale proceeds may already have been committed elsewhere. The practical answer is to consider the tax position before contracts are exchanged, not after completion.
Which capital gains deadline applies to you?
Capital Gains Tax, usually shortened to CGT, may arise when you make a profit on the disposal of an asset. A disposal does not only mean a straightforward sale. It can also include giving an asset away, transferring it to someone connected to you, exchanging it or receiving compensation, such as an insurance payment.
The deadline falls into two main categories. A UK residential property disposal that creates tax to pay has its own accelerated reporting and payment timetable. Most other capital gains are dealt with through Self Assessment after the end of the tax year.
That distinction matters. Waiting until January to deal with a gain on a buy-to-let sale could be far too late, whereas a gain on shares will often be reported as part of your tax return.
UK residential property: usually 60 days
If you are UK resident and sell or give away a UK residential property, you will normally need to report the gain and pay any Capital Gains Tax due within 60 days of completion where tax is payable. This commonly applies to a buy-to-let property, a holiday home or a former home that does not qualify fully for Private Residence Relief.
The report is made through HMRC’s online UK property service. It is separate from your Self Assessment return. If you are within Self Assessment, the disposal will usually still need to be included on your return as well, even where you have already reported and paid an estimated amount through the property service.
The 60-day period runs from completion, not from the date you receive all the proceeds, finish spending money on improvements or have time to gather paperwork. If completion takes place on 15 July, the deadline will fall in September. A delay in obtaining figures is not normally a reason to ignore the reporting requirement.
Non-UK residents have separate reporting duties when disposing of UK land or property, and a report can be required even where there is no tax to pay. The rules can be more involved, so it is sensible to take advice before completion rather than assume the standard 60-day rule covers your position.
Other assets: Self Assessment deadlines
For gains on assets such as shares, business assets, land that is not residential property, valuable possessions or certain investments, the normal route is Self Assessment. The gain is reported for the tax year in which the disposal occurs.
The UK tax year runs from 6 April to 5 April. If you dispose of shares on 20 November 2026, the gain falls into the 2026/27 tax year. If you already complete Self Assessment, the online return and any CGT payment are generally due by 31 January 2028.
If you do not normally file a tax return but have a taxable gain, you must tell HMRC that you need to register by 5 October after the end of the relevant tax year. Paper returns have an earlier deadline of 31 October, while online returns are due by 31 January. In practice, online filing gives more time, but leaving the calculation until January can make planning difficult.
Why the date of disposal matters more than payment date
Many people naturally focus on when the money arrives. For tax purposes, the key date is usually the contract date, not completion, for an unconditional sale contract. This can affect which tax year the gain falls into, the allowances available and when the tax must be reported.
Property reporting is a notable exception in terms of timing: the 60-day filing and payment window is linked to completion. That means a sale agreed near the end of one tax year and completed in the next can have two important dates to consider.
For example, contracts for a property sale may be exchanged on 28 March but completion may not take place until 30 April. The disposal may fall into the earlier tax year for CGT calculation purposes, while the property report deadline is measured from the April completion date. This is exactly the type of situation where a quick calculation before exchange can prevent avoidable pressure later.
Work out the likely gain before you commit
The taxable gain is not simply the sale price less the original purchase price. A proper calculation starts with the proceeds and deducts the acquisition cost, qualifying buying and selling costs, and allowable capital improvement expenditure. Estate agents’ fees, solicitors’ fees and Stamp Duty Land Tax paid on purchase may be relevant, depending on the circumstances.
Repairs are different from improvements. Replacing broken items or restoring a property to its original condition will often be treated as a revenue expense rather than capital expenditure. An extension or work that improves the property beyond its original state may be treated differently. The detail and supporting evidence matter.
You may also be entitled to reliefs. Private Residence Relief can reduce or remove a gain on your main home, although periods of letting, absence and multiple-property ownership can complicate the outcome. Business Asset Disposal Relief may be available on qualifying business disposals, but strict ownership, employment and trading conditions apply. Do not assume that being a company director automatically secures the relief.
Every individual has an annual exempt amount, but it is much smaller than it was a few years ago. Couples should also be careful before a sale. A transfer between spouses or civil partners can normally take place without an immediate CGT charge, and it may allow two annual exempt amounts or lower tax rates to be used. However, this needs to be planned before the disposal and should reflect genuine ownership and the wider financial position.
Be ready to make an estimated payment
The 60-day property report requires an estimate of the tax due. You need to consider your expected taxable income for the year because this can affect the CGT rate applied to part of the gain. You should also account for capital losses already realised in the year and any brought-forward losses that are available to use.
This can feel awkward if you do not yet know your final year-end income, particularly if you run a growing business with variable drawings, dividends or profits. But an estimate is still required. If the final calculation changes, the property report can usually be amended and the position reconciled through Self Assessment where appropriate.
The right approach is not to guess. Prepare a realistic forecast of income, dividends and known gains before the sale completes. This also helps you ring-fence enough of the proceeds for tax rather than finding the cash has been used for another investment, debt repayment or refurbishment project.
Common mistakes that create unnecessary cost
The most expensive errors are often administrative rather than complex. People miss the deadline because they believe their solicitor has handled the tax, assume no return is needed because they made little cash profit, or forget that a gift can count as a disposal at market value.
Other frequent issues include losing invoices for improvement works, overlooking a period when a property was let, applying the wrong tax year, and failing to include a property gain on Self Assessment after submitting the 60-day report. Where a property is jointly owned, each owner generally has their own reporting and payment responsibility for their share.
Interest can be charged on late payment, and penalties may apply for late reporting. More importantly, late action takes away options. Once contracts have been exchanged, restructuring ownership, timing a dividend or realising losses elsewhere may no longer have the intended tax effect.
A practical timetable before selling
As soon as a sale becomes likely, gather the original purchase completion statement, sale costs, records of capital improvements and details of ownership changes. Ask for a CGT estimate before exchange of contracts, particularly if the sale involves a rental property, a business premises, company shares or an asset held jointly with a spouse.
You should also consider the commercial side of the decision. A tax-efficient sale that leaves the business short of working capital may not be the right outcome. For company owners, the sale of assets held personally, assets held by the company and the sale of shares can each produce very different tax and cashflow results. The best route depends on your plans for retirement, reinvestment, succession and future income.
At RK & Co, we help clients turn these deadlines into a clear plan: what tax may be due, what records are needed, when payment must be made and how the transaction fits their wider financial goals. A conversation before contracts are signed is usually far more valuable than trying to repair the position after completion.
A capital gain can be part of a positive step – selling an investment, passing value to family or realising years of work in a business. Give the tax timetable the same attention as the sale itself, and you can make that step with greater confidence.