How to calculate gains on RSUs
Restricted Stock Units (RSUs) are taxed in two stages. At vest, their market value is treated as employment income — taxed through PAYE by your employer. After that, the shares are yours like any other holding, and any growth from that point is subject to Capital Gains Tax when you eventually sell. This guide covers the CGT side: how to find your cost basis and what happens with each of the three common options at vest.
The key rule: your cost basis is the value at vest
Because you already paid income tax on the shares' value when they vested, that vest-date market value becomes your CGT base cost. When you later sell, the gain is sale proceeds minus that base cost — so you're only taxed on growth after vest, never the whole value.
In the calculator, enter each vest as a buy at the vest-date price (in the vest currency, with the exchange rate on that day). Multiple vests of the same stock merge into one Section 104 pool, exactly like ordinary purchases.
The three options at vest
When RSUs vest, most companies give you a choice about how to handle the income tax that's due immediately:
- Vest and keep all shares — you pay the income tax from cash (or it's withheld from your salary). All shares land in your account.
- Sell to cover — the company sells just enough shares to pay the income tax. You keep the rest.
- Sell all immediately — every share is sold at vest and you receive cash. No shares are kept.
Each option has different CGT consequences. Let's walk through all three with real scenarios.
Vest and keep all shares
Sarah works at Amazon — she pays the income tax from savings and keeps every share
On 15 May 2026, 50 of Sarah's AMZN RSUs vest at $200.00 per share. She pays the income tax separately (from cash), so all 50 shares land in her brokerage account. Six months later, the price has risen and she sells all 50 at $240.00.
| Date | Type | Symbol | Qty | Price | Fees | Ccy | FX Rate | GBP Value |
|---|---|---|---|---|---|---|---|---|
| 15 May 2026 | Buy (Vest) | AMZN | 50 | $200.00 | $0.00 | USD | 1.27 | £7,874.02 |
| 10 Nov 2026 | Sell | AMZN | 50 | $240.00 | $4.99 | USD | 1.27 | £9,445.28 |
The vest — establishes cost basis
50 shares vest at $200.00 with an FX rate of 1.27 (USD per £1). Her base cost in GBP:
Section 104 pool now holds
50 shares in her Section 104 pool at £157.48 average. No CGT event yet — vesting is an income tax event only.
The sale — gain is growth since vest
On 10 November she sells all 50 at $240.00 (FX 1.27, $4.99 fee). Proceeds:
The gain is only the growth after vest
Sarah isn't taxed on the full £9,445.28 — only on the £1,571.26 the shares grew by between vest day and sale day. The £7,874.02 was already taxed as income.
Sell to cover
James works at Meta — the company sells 12 of his 30 shares to pay income tax
On 1 June 2026, 30 META RSUs vest at $550.00. The company immediately sells 12 shares at the same $550.00 to cover the income tax, leaving James with 18. Later in December he sells those 18 at $620.00.
| Date | Type | Symbol | Qty | Price | Fees | Ccy | FX Rate | GBP Value |
|---|---|---|---|---|---|---|---|---|
| 1 Jun 2026 | Buy (Vest) | META | 30 | $550.00 | $0.00 | USD | 1.27 | £12,992.13 |
| 1 Jun 2026 | Sell | META | 12 | $550.00 | $0.00 | USD | 1.27 | £5,196.85 |
| 15 Dec 2026 | Sell | META | 18 | $620.00 | $4.99 | USD | 1.27 | £8,787.01 |
The vest — all 30 shares enter at $550.00
All 30 shares vest at $550.00 (FX 1.27). This is a buy of 30 shares:
Same-day sell to cover — gain is near zero
12 shares are sold the same day at the same $550.00 price. Because it's a same-day sale at the vest price, the gain is essentially zero (the same-day rule matches this sell to the vest-day buy at the same cost).
Section 104 pool now holds
18 shares remain in the pool at £433.07 average (the same $550.00 cost in GBP). The sold-to-cover shares left with no gain.
Later sale — this is where the real gain happens
In December, James sells his remaining 18 META at $620.00 (FX 1.27, $4.99 fee). The gain is the growth from $550.00 to $620.00 — just like an ordinary share sale from the pool.
Why record the sell-to-cover if the gain is zero?
Because it's still a disposal. It reduces your holding (from 30 to 18 shares) and HMRC may ask for the record. The calculator handles this automatically when you enter the vest as a buy and the sell-to-cover as a same-day sell.
Sell all immediately
Priya works at Apple — she sells every share at vest and takes the cash
On 1 August 2026, 80 AAPL RSUs vest at $220.00. Priya opts to sell all 80 the same day at the same price ($4.99 fee). She wants cash, not shares.
| Date | Type | Symbol | Qty | Price | Fees | Ccy | FX Rate | GBP Value |
|---|---|---|---|---|---|---|---|---|
| 1 Aug 2026 | Buy (Vest) | AAPL | 80 | $220.00 | $0.00 | USD | 1.27 | £13,858.27 |
| 1 Aug 2026 | Sell | AAPL | 80 | $220.00 | $4.99 | USD | 1.27 | £13,854.34 |
Vest and sell on the same day
All 80 shares vest and are sold at $220.00 the same day. The same-day rule matches the sale to the vest — the cost and the proceeds are essentially the same price, so the gain is near zero (just the tiny difference from the $4.99 fee).
Selling everything at vest usually means near-zero CGT
Because you sell at the same price you “bought” (vested), there's no growth to tax. The tiny loss here is just the broker fee. This is the simplest case for CGT — but you still need to record it as a disposal if it crosses the reporting threshold.
What to remember
- Your CGT cost basis is the market value at vest — enter it as a buy at that price.
- Sell to cover is a same-day disposal at (about) the vest price — gain is near zero, but it's still a recordable event.
- Sell all at vest means gain is near zero — the only CGT you'll ever owe is the rounding from fees and FX.
- Keep and sell later is where real gains arise — you're taxed on the growth between vest day and sale day.
- Multiple vests of the same stock merge into one Section 104 pool — later sales draw on the blended average cost across all your vests.
Related: the same-day rule (explains sell-to-cover matching), the Section 104 pool (how multiple vests combine), or rates & allowances.
Sources
The rules and figures in this guide come from HMRC and GOV.UK. This site is independent and not affiliated with HMRC.
- GOV.UK — Tax when you sell shares — When CGT applies to selling shares and units, and which disposals are exempt.
- HMRC Capital Gains Manual CG51560 — The same-day rule (TCGA92/S105) and the 30-day 'bed and breakfast' rule (TCGA92/S106A), with worked examples.
- HMRC Capital Gains Manual CG51575 — The Section 104 holding (pool) in detail: pooled cost and part-disposal apportionment.