Share Incentive Plan (SIP) Calculator
This Share Incentive Plan (SIP) calculator works out the upfront Income Tax and National Insurance saving from buying UK SIP partnership shares, or what you’d owe if you take shares out of the plan before the 5-year mark. Enter your figures and it shows the result instantly, with the underlying HMRC rules behind each number.
Also known as: SIP calculator, share incentive plan calculator, employee share scheme calculator, partnership shares calculator, SIP tax calculator.
Buying UK SIP partnership shares saves your marginal Income Tax + NI rate on the amount contributed, since it comes out of gross salary. Withdraw within 3 years and tax is due on the full value; between 3–5 years, on the lower of acquisition and withdrawal value; after 5 years, no Income Tax or NI is due at all. This calculator covers SIPs specifically — not LTIPs or stock options, which work differently (see below).
taxable amount × (Income Tax + NI rate)Why Use a Share Incentive Plan Calculator
A Share Incentive Plan lets employees buy company shares straight out of their gross salary, before Income Tax and National Insurance are worked out — which means the real cost of a SIP contribution is always lower than the number on the payslip. A SIP calculator makes that saving concrete: instead of estimating your marginal rate by hand, you pick your tax band and see exactly how much of each pound going into partnership shares would otherwise have gone to HMRC.
The trickier side of a SIP is what happens on the way out. Withdraw shares within 3 years and Income Tax and NI are due on their full value at withdrawal; withdraw between 3 and 5 years and it’s due on the lower of the value at acquisition and at withdrawal instead; hold for 5 years or more and no Income Tax or NI is due at all. Because those three outcomes can produce very different net figures for the same shares, this calculator’s “Withdrawing Shares” mode exists specifically to compare them before you decide whether to hold on or cash out.
Because SIP rules combine an employer’s specific scheme design with HMRC’s national limits and tax bands, no calculator can replace reading your own scheme documentation. What this tool does is remove the arithmetic, so the only thing left to check against your actual plan rules is whether a good-leaver exception or a different holding period applies to your situation.
The Four Share Types, and What the Holding Period Changes
A SIP can combine up to four share types, and the tax treatment on the way out depends entirely on how long shares sat in the plan trust.
Free, partnership & matching shares
Employers can give up to £3,600 of free shares a year; employees can buy up to £1,800 (or 10% of salary, whichever is lower) of partnership shares from pre-tax salary; employers can match those 1-for-1 or 2-for-1, free of charge.
Why partnership shares save tax immediately
Because the contribution comes out of your salary before Income Tax and NI are calculated, you effectively buy the shares at a discount equal to your marginal tax + NI rate.
The 3-year and 5-year marks
Withdraw before 3 years and Income Tax + NI is due on the full value at withdrawal. Withdraw between 3–5 years and it’s due on the lower of the value at acquisition and at withdrawal. Hold 5+ years and there’s no Income Tax or NI at all.
“Good leaver” exceptions
Leaving due to death, injury, disability, redundancy, retirement, or a TUPE transfer generally means no Income Tax or NI is due on withdrawal, regardless of how long shares were held.
SIP vs. Long-Term Incentive Plan (LTIP) vs. Stock Options
These three terms get searched together because they’re all forms of UK employee equity reward, but they work quite differently — and only one of them has a fixed formula this calculator can model.
Share Incentive Plan (SIP)
A statutory, HMRC-defined scheme with fixed annual limits and a fixed holding-period tax rule that applies the same way at every participating employer. That’s exactly why a calculator can model it accurately.
Long-term incentive plan (LTIP)
An LTIP is a company-designed reward, usually for senior staff, with its own performance conditions, vesting schedule, and share or cash structure. There’s no single statutory formula — each employer’s LTIP rules are different, so a generic LTIP calculator can’t give a meaningfully accurate result the way a SIP calculator can.
Share options (e.g. EMI, CSOP)
A share option gives the right to buy shares later at a fixed price, taxed differently (often under EMI or CSOP rules) from SIP shares, which are actual shares held now. If you’re looking at a stock option payout, the tax treatment and timing depend on the specific option scheme — an accountant or your scheme’s own documentation is the reliable source here, not a general calculator.
SIP Calculator: Worked Examples
Three common scenarios worked end-to-end using the same rules as the calculator above.
Basic-rate taxpayer buying partnership shares with 2-for-1 matching
A basic-rate employee on a £45,000 salary puts £1,800 a year into partnership shares, with 2-for-1 employer matching. What’s the effective cost versus the total value received?
Given inputs
- Salary: £45,000
- Partnership shares: £1,800/year
- Matching: 2 shares per 1 bought
- Tax band: Basic rate (28% combined)
Computed outputs
- Tax & NI saved: £1,800 × 28% = £504
- Matching shares value: £1,800 × 2 = £3,600
- Total shares value: £1,800 + £3,600 = £5,400
- Effective cost: £1,800 − £504 = £1,296, for £5,400 of shares
Higher-rate taxpayer withdrawing shares within 3 years
A higher-rate taxpayer’s shares were worth £1,800 at acquisition and have grown to £2,400. They leave the plan after 2 years. What’s the net value after tax?
Given inputs
- Value at acquisition: £1,800
- Value at withdrawal: £2,400
- Holding period: Under 3 years
- Tax band: Higher rate (42% combined)
Computed outputs
- Taxable amount: £2,400 (full value at withdrawal)
- Income Tax & NI due: £2,400 × 42% = £1,008
- Net value after tax: £2,400 − £1,008 = £1,392
- Under-3-year withdrawals are taxed on the full current value, not the lower acquisition value.
Basic-rate taxpayer withdrawing after 4 years, share price down
A basic-rate taxpayer’s shares were worth £2,000 at acquisition but have fallen to £1,500 after 4 years. What’s the taxable amount and net value?
Given inputs
- Value at acquisition: £2,000
- Value at withdrawal: £1,500
- Holding period: 3–5 years
- Tax band: Basic rate (28% combined)
Computed outputs
- Taxable amount: lower of £2,000 and £1,500 = £1,500
- Income Tax & NI due: £1,500 × 28% = £420
- Net value after tax: £1,500 − £420 = £1,080
- The 3–5 year rule protects against tax on a value the shares no longer hold.
SIP Calculator Mistakes to Avoid
Assuming the £1,800 partnership share cap always applies
The actual annual limit is the lower of £1,800 or 10% of salary. An employee earning £15,000 a year has a cap closer to £1,500, not £1,800 — check the calculator’s cap note against your own salary.
Mixing up “value at acquisition” for different share types
For partnership shares, this is usually the price paid. For free or matching shares, there’s no purchase price — “value at acquisition” instead means the market value when the shares entered the plan.
Assuming a good-leaver exception applies automatically
Good-leaver status depends on the specific reason for leaving and the employer’s scheme rules, not just on the calculator’s toggle. Confirm the classification with your scheme administrator before relying on a tax-free withdrawal.
Using UK-wide bands for a Scottish taxpayer
Scottish Income Tax has its own bands and rates that differ from England, Wales, and Northern Ireland, even though National Insurance is calculated the same way UK-wide. A Scottish taxpayer’s actual figure may differ from this calculator’s estimate.
Applying this calculator to an LTIP or share option instead of a SIP
LTIPs and share options (like EMI or CSOP) are taxed under different rules than SIPs, and LTIPs in particular vary by employer with no fixed formula. Using SIP figures to estimate an LTIP or option payout will give a misleading number.
SIP Calculator FAQ
What’s the maximum I can get through a SIP in one year?
+
What’s the difference between a SIP and a long-term incentive plan (LTIP)?
+
Does this calculator work out stock option tax?
+
Why does the calculator ask for my tax band as a combined percentage?
+
What happens to shares I keep for 5+ years?
+
Can I lose my matching shares?
+
Does this apply if I’m a Scottish taxpayer?
+
Should I talk to an accountant about my SIP shares?
+
About This Calculator
I’m Umer Farooq, the founder of calcsdone and the person who built and maintains this SIP calculator. I’m not a tax advisor — I check the limits, tax bands, and holding-period rules on this page directly against GOV.UK and HMRC guidance, linked below, and update it whenever those figures change for a new tax year. If something looks off, get in touch or find me on LinkedIn.
More Calculators Like This
calcsdone’s other finance calculators are currently US-focused (paycheck and federal retirement tools), so there isn’t yet a closely related UK scheme calculator to point to beyond the category page below.
SIP Calculator: References
- Tax and Employee Share Schemes: Overview. GOV.UK.
- Share Incentive Plans: A Guide for Employees. GOV.UK.
- Income Tax Rates and Personal Allowances. GOV.UK.
- National Insurance Rates and Categories. GOV.UK.
- HS287: Capital Gains Tax and Employee Share Schemes. GOV.UK.
- Enterprise Management Incentives (EMI). GOV.UK.