UK Capital Gains Tax — SA108 & 60-Day Property Return

Establish the client's UK tax residency status, identify every disposal made in the tax year (6 April to 5 April), and classify each asset type — shares, residential property, commercial property, crypto, or business assets. Residency determines whether CGT applies and whether the 60-day reporting obligation is triggered for non-residents. Disposals include gifts, exchanges, and part-disposals, not just cash sales.

For each disposal, gather the original acquisition cost and all allowable incidental costs. For shares and crypto, apply the TCGA 1992 share-matching rules (same-day, 30-day bed-and-breakfasting, then Section 104 pool average cost). For property, identify enhancement expenditure (capital improvements) that can be added to the cost base. Confirm that no allowable costs have been omitted or double-counted.

Assess every available relief against each disposal before computing tax. Key reliefs are: Principal Private Residence (PPR) relief and Letting Relief for residential property; Business Asset Disposal Relief (BADR) or Investors' Relief for qualifying business disposals; no-gain/no-loss treatment for spouse/civil partner transfers; EIS/SEIS deferral or exemption; and the £3,000 Annual Exempt Amount. Document the basis for each relief claimed.

Where a UK residential property has been sold and CGT is due, a separate CGT on UK Property return must be filed online with HMRC within 60 days of completion. The CGT must also be paid within that 60-day window. This step is mandatory before the annual SA100/SA108 filing. Failure to file within 60 days triggers an initial £100 penalty under TMA 1970, with further accruing penalties. The amount paid is then credited on the SA return to avoid double taxation.

Apply current-year losses against current-year gains (this is mandatory and cannot be waived even if it wastes the Annual Exempt Amount). Then offset brought-forward losses only to the extent needed to reduce net gains to the £3,000 Annual Exempt Amount — never below it, to preserve the benefit of the AEA. Report any unused losses to HMRC on SA108 or by letter to make them available for carry-forward. Losses on disposals to connected persons are ring-fenced and can only be set against gains on disposals to the same connected person.

Compute the final CGT liability by allocating gains to the correct rates. Rates depend on the disposal date (post-30 October 2024: 18%/24% for all assets; BADR 14% in 2025-26 and 18% from 6 April 2026) and on how much unused Income Tax basic rate band (£50,270 threshold) the client has after accounting for taxable income. Residential property and non-residential gains use the same 18%/24% rate structure from 30 October 2024 onwards. Produce a final CGT summary showing tax due.

Complete the SA108 Capital Gains Tax Summary supplementary pages and attach them to the SA100 Self Assessment tax return. Enter total chargeable gains, total allowable losses, the Annual Exempt Amount, BADR/IR claims, and any credit for CGT already paid via the 60-day property return. Submit by 31 January following the end of the tax year (31 January 2026 for 2024-25). Retain all supporting schedules and cost-base evidence for at least 6 years in case of HMRC enquiry.