If your employer has offered you shares through a Share Incentive Plan (SIP), your first instinct might be to search for a Share Incentive Plan calculator for private company employees to work out what those shares are actually worth.
But here's the catch: most SIP calculators online are built for listed companies with a live, public share price. Private companies don't have that luxury.
Does the calculator still hold up?
Yes, but with adjustments. In this article, we'll break down how a SIP calculator works when your company isn't publicly traded, what makes the valuation different, and what you need to know about eligibility and tax before you rely on any numbers.
What Makes SIP Calculators Different for Private Company Share Schemes
Standard SIP calculators pull a real-time share price to estimate your holding's value. Private company share schemes don't have that reference point, because there's no stock exchange listing to check.
Instead, private companies rely on an agreed valuation, typically set by:
An independent valuation specialist
HMRC's Shares and Assets Valuation (SAV) team, via a formal agreement
The company's own board, based on financial performance and comparable sales
A calculator can still work here, but only if you manually input this agreed value rather than expecting the tool to fetch it automatically. Getting this step wrong is one of the more common SIP mistakes to avoid.
SIP Eligibility Rules for Private Company Employees
Before worrying about valuation, it's worth confirming eligibility. SIP eligibility rules apply the same way whether a company is listed or private:
You must be an employee of the company (or a qualifying subsidiary)
The scheme must be offered to all eligible employees on similar terms
There's typically a minimum employment period before you can participate
Private companies can and do offer SIPs; it's simply less common than at large listed firms, mainly because of the added valuation work involved. If you're weighing this scheme against alternatives, it's worth reading how SIP vs SAYE compares before committing.
SIP Share Valuation: Why It's the Real Challenge
This is where things get tricky. SIP share valuation for a private company isn't a one-time task; it needs to happen every time shares are awarded and again whenever shares are sold or leave the scheme.
Because private company shares are illiquid, valuations often factor in:
Recent funding rounds or investment activity
Company revenue and profitability trends
Discounts for minority shareholding or lack of marketability
Independent Share Valuation for SIP Awards
Many private companies use an independent valuer specifically to keep the process defensible for HMRC purposes.
This protects both the employer and employee if the valuation is ever questioned.
Illiquid Shares Tax Implications
Because there's no open market, illiquid shares' tax implications can catch employees off guard. You may hold shares worth a certain "paper value" with no easy way to sell them until an exit event, such as an acquisition or IPO, yet tax rules still apply based on that valuation.
SIP Tax Benefits: What Still Applies
The good news is that SIP tax benefits are unaffected by whether your company is private or listed, provided the scheme is HMRC-approved. If you hold your shares for the required period, you can benefit from:
No Income Tax or National Insurance on shares held for 5+ years
Tax-free growth in value while shares remain in the plan
Reduced Capital Gains Tax if shares are sold directly from the plan
SIP Holding Period Rules and Leaving Employer with SIP Shares
Holding periods matter more with private companies, since exit opportunities (like a sale) are less predictable than simply selling on a public exchange.
If you're leaving your employer with SIP shares before the holding period is complete, you may lose some tax advantages, and the company may buy back your shares at the last agreed valuation rather than a market price.
For the full rules on what happens to unvested or partially held shares, check the forfeiture rules when leaving your job.
Frequently Asked Questions
Can private companies offer a share incentive plan?
Yes, private companies can offer a share incentive plan to employees, following the same HMRC eligibility rules as listed companies.
How is SIP share valuation done for private companies?
SIP share valuation for private companies is typically carried out by an independent valuer or agreed with HMRC's Shares and Assets Valuation team. This valuation is then used as the reference price whenever shares are awarded or removed from the plan.
Does a SIP calculator give an accurate value for private company shares?
A SIP calculator gives an accurate estimate only if you input the correct, up-to-date agreed valuation manually. Since private shares aren't traded publicly, the calculator can't automatically pull a real-time price like it would for a listed company.
What happens to my SIP shares if I leave my employer?
If you're leaving your employer with SIP shares before the required holding period, you may lose some SIP tax benefits, and your shares are often bought back at the last agreed valuation. Timing your exit around the holding period can help preserve tax advantages.
Are SIP tax benefits different for private company employees?
No, SIP tax benefits apply the same way for private and listed company employees, as long as the scheme is HMRC-approved.