Guide

SA108 for Shares: How to Fill In Boxes 23 to 30 on Your 2025/26 Return

Reviewed by the UKCapitalGainsTaxCalculator team · Last checked 3 November 2026 Box numbers checked against HMRC's SA108 notes 2026 (tax year 2025-26)

Quick answer

Sales of listed shares, UK OEICs and authorised unit trusts go in boxes 23 to 30 of the Capital Gains Tax summary (SA108). You enter totals for the year: number of disposals (23), proceeds (24), allowable costs (25), gains before losses (26) and losses (27), plus a claim code (28) and any real-time service gains and tax (29 and 30). Do not take off the £3,000 allowance; HMRC applies it.¹ The 2025/26 return is due online by 31 January 2027.⁶

Key facts

Sales of the same class of shares in the same company on the same day count as one disposal in box 23.¹
AIM shares and shares under EIS, SEIS or employee shareholder status are unlisted: boxes 31 to 44.¹
Box 26 must include gains in box 29, and box 27 must include losses in box 29.¹
Losses from earlier years go in box 45, and only bring this year's gains down to £3,000; the rest goes in box 47.¹⁵
Send a computation for each disposal; HMRC says not to write "see attached" in the boxes.¹

Listed or unlisted: which section?

HMRC's notes put three kinds of holding in the listed section: shares or securities in a company listed on a recognised stock exchange, shares in a UK open-ended investment company, and units in an authorised unit trust.¹ Everything else is unlisted (boxes 31 to 44), including shares on the Alternative Investment Market. The unlisted section is also used for all shares where Employee Shareholder Status, the Enterprise Investment Scheme or Seed Enterprise Investment Scheme apply, where share loss relief is claimed against income, and for disposals to Employee Ownership Trusts.¹

Cryptoassets have their own section (boxes 13.1 to 13.8), and shares in an ISA are not reported at all.¹

Boxes 23 to 30, one by one

Listed shares and securities, SA108 2025/26

Box	What goes in it
23 Number of disposals	Disposals in the year. Same class, same company, same day = one disposal. Leave out disposals you make as a trustee.
24 Disposal proceeds	Total proceeds, before any reliefs, claims or elections.
25 Allowable costs	Total allowable costs, including the purchase price (for most holdings, the Section 104 pool cost of the shares sold).
26 Gains in the year, before losses	Total of your gains, after reliefs that reduce gains. Do not take out gains taxed at a different rate under BADR or Investors' Relief. Must include gains in box 29.
26.1 FIG regime claim	Only if you claim the foreign income and gains regime on the SA109.
27 Losses in the year	Total of your losses, after reliefs. Must include losses in box 29.
28 Claim or election code	A 3-letter code if you make a claim, for example NVC for a negligible value claim or ESH for employee shares (MUL if more than one), with details in box 54.
29 Real-time returns	The overall gain or loss on listed shares you already reported through the real-time service (a minus sign for a loss).
30 Tax already paid	The tax you paid on the box 29 gains through the real-time service.

From HMRC's Capital Gains Tax summary notes for 2025/26, pages CGN 4 and CGN 8.¹ Real-time reference numbers go in box 54.

Worked example: a gain and a loss in 2025/26

Tom earns a £55,000 salary. In October 2025 he sold units in a UK fund for £30,000 (pool cost £21,500), and in February 2026 he sold shares in a listed company for £12,000 (pool cost £15,200). Total proceeds are £42,000, under £50,000, but his gains before losses of £8,500 are over £3,000, so he needs the capital gains pages.¹

Tom's listed shares boxes

Box 23 Number of disposals	2
Box 24 Disposal proceeds (£30,000 + £12,000)	£42,000
Box 25 Allowable costs (£21,500 + £15,200)	£36,700
Box 26 Gains before losses (fund)	£8,500
Box 27 Losses (shares)	£3,200
Boxes 28 to 30	Blank

What HMRC's calculation then gives

Net gain (£8,500 − £3,200)	£5,300
Less annual exempt amount (applied automatically)	−£3,000
Taxable gain	£2,300
CGT at 24% (his salary uses up the basic-rate band)	£552.00

2025/26 rates: 18% within the unused basic-rate band and 24% above it, after the £3,000 allowance.⁴ Same-year losses come off first.⁵ Tom attaches a computation for each sale.¹

Already used the real-time service?

If you are in Self Assessment you must still put a sale on your return after reporting it through the real-time service.³ Put the overall gain or loss on those listed shares in box 29 and the tax you paid in box 30, and make sure the same gains and losses are inside your box 26 and box 27 totals. The reference numbers of each real-time submission go in box 54.¹

Gains on unlisted shares reported in real time go in boxes 37 and 38 instead, and cryptoassets in boxes 13.7 and 13.8.¹

Losses: boxes 45 and 47

Box 45, losses brought forward and used in-year: earlier losses can only reduce your gains to the annual exempt amount, £3,000 for individuals in 2025/26.¹
Box 47, losses available to carry forward: the total of unused losses to take into later years.¹
A loss must be claimed within 4 years of the end of the tax year you made it: a 2025/26 loss by 5 April 2030.⁵ See how to claim a capital loss.

Box 53, box 54 and what to attach

Put an X in box 53 if your computations include estimates or valuations, and explain them in box 54 or your computation.¹ Box 54 also takes the details of any claim, the real-time reference numbers and anything else that supports your figures. HMRC asks you to send your computations, valuations and claim forms with the pages, fill in every box that applies, and not cross through boxes or write "see attached" in them.¹

For the share matching rules behind each figure (same day, 30 days, then the pool), see HMRC's helpsheet HS284 and our 30-day rule guide.²

Get the pool cost for box 25

The Section 104 pool tracker applies the same-day and 30-day rules and gives the cost of the shares you sold.

Open the share pool tracker

Frequently asked questions

Which SA108 boxes are for shares?

Listed shares and securities go in boxes 23 to 30: shares in companies listed on a recognised stock exchange, UK OEICs and authorised unit trusts. Unlisted shares, including AIM shares and shares under EIS, SEIS or employee shareholder status, go in boxes 31 to 44.

Do I enter each sale separately on the SA108?

No. The boxes take totals for the year: number of disposals, total proceeds, total allowable costs, total gains and total losses. You send a separate computation for each disposal with the return. Sales of the same class of shares in the same company on the same day count as one disposal.

Do I take off the £3,000 allowance in the shares boxes?

No. HMRC's notes say not to deduct the annual exempt amount; it is given automatically. Box 26 is gains before losses and box 27 is losses, both before the allowance.

I reported a share sale through the real-time service. What goes in boxes 29 and 30?

Box 29 is the overall gain or loss on listed shares you reported through the real-time service, and box 30 is the tax you paid on it. The same gains and losses must also be in the box 26 and box 27 totals, and the real-time reference numbers go in box 54.

Where do I put losses from earlier years?

Box 45, losses brought forward and used this year. HMRC's notes say these can only reduce your gains down to the annual exempt amount (£3,000 for 2025/26). Unused losses to carry forward go in box 47.

Where do funds and investment trusts go?

HMRC's notes put units in authorised unit trusts and shares in UK OEICs in the listed section, along with shares in companies listed on a recognised stock exchange. Shares and funds inside an ISA are not reported at all.

This page is general information, not tax advice. Box numbers are from HMRC's 2025/26 Capital Gains summary notes (SA108 Notes 2026) as checked on 3 November 2026.

Sources & references

The rates, allowances and rules in this guide are drawn from the official HMRC and GOV.UK sources below, checked for the 2026/27 tax year. Each link opens the relevant government page in a new tab.

Verified against published HMRC and GOV.UK guidance.