When is the tax on an RSU vest due?

Income tax and NI are collected through PAYE at vest. Any shortfall (the true-up) is paid through self-assessment, with the balancing payment due by 31 January after the tax year.

Should I sell my RSUs as soon as they vest?

Selling at vest crystallises little or no capital gain and reduces single-company risk. Holding can build a future CGT bill on the growth. It is a personal risk decision; this tool shows the tax side.

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RSU & equity

What to Do After a Large RSU Vest

5 min read. Last verified 23 June 2026. 2026/27 rules.

The short answer

After a large RSU vest: work out the true-up between your real tax and what your employer withheld, set that cash aside for self-assessment, decide whether to hold or diversify, and note the vest-date value as your CGT cost base.

Key facts

Sell-to-cover is often a flat ~47%; your real rate can be 60% in the £100k–£125,140 band.
The self-assessment balancing payment is due by 31 January after the tax year.
Your CGT cost base is the vest-date value, so future gains are measured from there.

A large vest is both a windfall and a tax event. The mistake is spending or reinvesting all of it before the real tax position is clear, then being short when the self-assessment bill lands.

Step 1: find the true-up

Compare the tax actually due on the vest with what your employer withheld through sell-to-cover. If your real marginal rate is above the flat withholding rate, you have under-withheld and owe the difference.

Step 2: consider reserving the amount

One approach many people take is to set the true-up figure aside in a separate savings account until self-assessment. The balancing payment is due by 31 January following the tax year.

Step 3: decide whether to hold

Holding concentrates risk in one company; diversifying reduces it.
Selling at vest crystallises little or no capital gain.
Holding a rising share builds a future CGT bill on the growth.
Consider moving shares into an ISA or pension where possible.

Common questions

When is the tax on an RSU vest due?: Income tax and NI are collected through PAYE at vest. Any shortfall (the true-up) is paid through self-assessment, with the balancing payment due by 31 January after the tax year.
Should I sell my RSUs as soon as they vest?: Selling at vest crystallises little or no capital gain and reduces single-company risk. Holding can build a future CGT bill on the growth. It is a personal risk decision; this tool shows the tax side.

Related playbooks

Sources

GOV.UK: Self Assessment deadlines

Figures verified against gov.uk and gov.scot on 30 June 2026. Constants version 2026/27.3. 2026/27 tax year. This is a modelling tool for general insight, not financial or tax advice.