3-Month SONIA Index Futures Contract Specifications (SO3)
Interest rate futures quote in price points that map to a fixed dollar value per contract. Small quote increments matter here more than in most markets, because a rate move of a few basis points translates into a meaningful P/L swing on a full-size contract.
Specifications
| Contract unit | £500,000 |
| Exchange | ICE Europe - Financials |
| Symbol | SO3 |
| Tick size | 0.005 |
| Tick value | £6.25 |
| Point value | £1,250 |
| Delivery months | H,M,U,Z |
| Sector | Financials |
| Quote currency | £ |
Margin is not listed here on purpose — the exchange revises it and every broker adds its own buffer. Check your broker's platform for the live figure. Use the margin calculator to estimate what a position will tie up.
Doing the tick math
One tick is 0.005 in the quoted price, which is £6.25 per contract. A move of one full point (1.00 in the quoted price) is worth £1,250, so there are 200 ticks in a point. Get those two numbers wrong and every risk calculation downstream is wrong, which is the point of the tick value guide.
Enter your own prices in the tick value and P/L calculator to see the dollar result for this contract without doing the arithmetic by hand.
Delivery months
H,M,U,Z — March, June, September, December. Liquidity concentrates in the nearest active month; open interest migrates over a few weeks before expiry, which is what the roll mechanics guide walks through.
What one tick is worth at different position sizes
The per-tick figure scales linearly, which is the part most traders get wrong when they add contracts without re-checking risk.
| Position | Value of 1 tick | Value of 10 ticks |
|---|---|---|
| 1 contract | £6.25 | £62.50 |
| 2 contracts | £12.50 | £125 |
| 5 contracts | £31.25 | £312.50 |
| 10 contracts | £62.50 | £625 |
Ten ticks on a SO3 contract is a move of 0.005 × 10 in the quoted price. If you want the P/L for a specific entry and exit rather than a tick multiple, put the prices into the tick value calculator.
Converting your stop into a dollar risk
Stops are set in price terms but risk is booked in dollars. Multiply the stop distance in ticks by the tick value — and then add commission, which is charged per contract per side and is not in the numbers below.
| Stop distance | 1 contract | 5 contracts |
|---|---|---|
| 5 ticks | £31.25 | £156.25 |
| 10 ticks | £62.50 | £312.50 |
| 20 ticks | £125 | £625 |
| 40 ticks | £250 | £1,250 |
On a £500,000 contract, a 20-tick stop at one contract ties up £125 of risk before costs. At five contracts it is £625. This is why position size should follow the stop, not the other way round — the arithmetic is laid out in choosing a futures contract.
How margin is set on 3-Month SONIA Index futures
Margin is not a property of the contract spec — it is a risk parameter the exchange recalculates periodically and that your broker then marks up. Two consequences follow:
- The figure moves when volatility moves, so a margin number copied from a blog post is usually stale.
- Two brokers can require different amounts for the same SO3 contract.
What is fixed by the spec is the notional exposure: £500,000 multiplied by the price. Margin is a percentage of that notional, which is why a higher price or a wider exchange buffer raises the cash requirement without the contract itself changing. The margin calculator takes your broker's number and converts it into "how many contracts can I hold"; the mechanics are in how futures margin works.
Where these numbers come from
Contract unit, tick size and delivery months are taken from the contract specifications published by ICE Europe - Financials. Exchanges occasionally change tick sizes and listing months, so before relying on this page for a live position, check the current spec sheet on the exchange's own product page or on your broker's platform. This page was last rebuilt on 15 November 2026.
What moves 3-Month SONIA Index prices
- The policy rate path — expectations for central bank decisions drive the front end
- Inflation prints — the main input to that path
- Supply and auctions — issuance calendars move the long end
- Flight to quality — risk-off flows bid the complex regardless of fundamentals
This is context, not a recommendation. Nothing here tells you which way the market is going.
More financials contracts
- Euro-Schatz (FGBS) — 100,000 €, €5 per tick
- 3-Year U.S. Treasury Note (Z3N) — $200K note, $7.81 per tick
- 5-Year U.S. Treasury Note (ZF) — $100K note, $7.81 per tick
- 2-Year U.S. Treasury Note (ZT) — $200K note, $7.81 per tick
- Long-Term Euro-BTP (FBTP) — 100,000 €, €10 per tick
- Short-Term Euro-BTP (FBTS) — 100,000 €, €10 per tick
Full list: all 135 contract specifications. Sizing maths: tick value calculator, margin calculator.
Frequently asked
What is the contract size of 3-Month SONIA Index futures?
One SO3 contract represents £500,000. Every tick value and point value on this page follows from that quantity.
How much is one tick worth in SO3 futures?
One tick is a price move of 0.005, worth £6.25 per contract. A full point move (1.00 in the quoted price) is worth £1,250.
Which delivery months does SO3 trade?
H,M,U,Z — March, June, September, December. The front month carries most of the liquidity and open interest migrates a few weeks before expiry.