Options Capital Gains Tax in the UK — How HMRC Taxes Calls, Puts, and Assignments

Options trading is growing fast among UK retail investors, but the tax guidance is thin on the ground. HMRC’s own manual pages on derivatives are sparse, and most UK CGT calculators ignore options entirely. If you’re trading calls and puts on Robinhood UK or Tastytrade, here’s what you actually need to know.

The basic principle: options are chargeable assets

Under HMRC rules, traded options are chargeable assets — just like shares. When you dispose of an option (by closing it, letting it expire, or having it assigned/exercised), a capital gain or loss arises. The relevant legislation is TCGA 1992, section 144, with HMRC guidance at CG12300 and CG55500.

Options go in a different section of the SA108 than shares. While listed shares are in Boxes 23-30 (“Listed shares and securities”), options belong in Boxes 14-22 (“Other property, assets and gains”). Getting the box wrong won’t cause a tax penalty, but it may trigger questions from HMRC.

How each scenario is taxed

Buying and selling options (BTO → STC or STO → BTC)

The simplest case. You open a position and close it later. The gain or loss is the difference between what you paid and what you received.

Long option (Buy to Open → Sell to Close):

Short option (Sell to Open → Buy to Close):

Options of the same type (same underlying, same expiry, same strike, same call/put) are “identical” for matching purposes. If you have multiple opens, closes are matched on a FIFO (first-in-first-out) basis — oldest open first.

Options expiring worthless

If a long option expires worthless, you realise a loss equal to the premium you paid. The disposal proceeds are zero.

If a short option expires worthless, you realise a gain equal to the premium you received. The cost is zero.

In both cases, the expiry date is the disposal date. This matters for determining which tax year the gain or loss falls into.

Assignment and exercise — the tricky part

This is where HMRC’s rules are genuinely complex. Under TCGA s.144(2) and (3), the grant of an option and its exercise are treated as a single transaction. In practice, this means:

Written call gets assigned: You sold a call, and the buyer exercised it. You’re obligated to sell shares at the strike price. The option premium you received when you wrote the call gets added to the stock sale proceeds. There’s no separate option disposal — the option gain/loss is £0, and the premium rolls into the stock trade.

Written put gets assigned: You sold a put, and the buyer exercised it. You’re obligated to buy shares at the strike price. The option premium you received gets deducted from the stock acquisition cost. Again, no separate option disposal.

Long call exercised: You bought a call and exercise it to acquire shares. The premium you paid gets added to the stock acquisition cost.

Long put exercised: You bought a put and exercise it to sell shares. The premium you paid gets added to the disposal costs (reducing proceeds).

Getting this wrong is one of the most common errors in UK options tax. If you treat the assignment as a separate option disposal and also include the stock trade at face value, you’re double-counting the premium — once as an option gain and again in the stock proceeds.

Covered calls and cash-secured puts

These are the most common option strategies for UK retail investors. The tax treatment follows directly from the rules above.

A covered call (you own the shares and sell a call against them) results in one of three outcomes:

The call expires worthless → you keep the premium as a gain (reported as an option disposal).

You buy the call back to close → gain or loss is the net of premiums.

The call gets assigned → no option gain, premium added to stock sale proceeds.

A cash-secured put (you sell a put and keep cash aside to buy if assigned) works the same way — premium income on expiry/close, or premium reduction to stock cost on assignment.

Exchange rates for option trades

Same rule as shares: use HMRC’s monthly exchange rate for the month of each transaction. The opening trade converts at its month’s rate. The closing trade (or expiry, or assignment) converts at that month’s rate. Each leg uses a potentially different rate.

Fees on option trades

On Robinhood UK, option trades incur:

Commission: $0.50 per contract (after promotional period)

Options Regulatory Fee: $0.04 per contract

Trading Activity Fee: applies to sells (STO, STC) only

These are allowable costs — added to the cost of buying options, deducted from the proceeds of selling options.

Reporting on SA108

Option gains and losses go in the “Other property, assets and gains” section of SA108 (Boxes 14-22), not the listed shares section. This is because HMRC classifies traded options as derivatives, not securities.

The boxes work the same way as the shares section: total disposals in Box 14, proceeds in Box 15, costs in Box 16, gains in Box 17, losses in Box 18.

If an option was assigned or exercised and the premium was merged into a stock trade, the stock trade goes in the listed shares section (Boxes 23-30) with the adjusted cost/proceeds. The option event itself shows as £0 gain in the options section.

Using TaxBull for options CGT

We built TaxBull specifically to handle these cases. It’s the only free UK CGT calculator that supports the full option lifecycle — BTO, STO, BTC, STC, OEXP, OASGN, and OEXCS — with correct TCGA s.144 treatment for assignments and exercises. It automatically separates option events from stock disposals and maps them to the correct SA108 boxes.

Upload your Robinhood UK or Tastytrade CSV, and the options CGT is calculated alongside your share gains with a full audit trail showing exactly how each position was matched.

This article is for informational purposes only. HMRC guidance on derivatives taxation is limited and individual circumstances vary. Always consult a qualified tax professional for advice specific to your situation.