YieldSmart is built on standard fixed-income maths, applied with UK tax rules. This page sets out exactly how each figure is derived, what we assume, where our data comes from, and — just as importantly — what we don't model. If a number ever looks wrong, this is the page to check it against.
Last reviewed: 2 November 2026. We update this page whenever a calculation changes.
During London Stock Exchange trading hours prices are indicative mid prices — halfway between the bid and offer quoted on the LSE (delayed at least 15 minutes by the exchange), refreshed about every 10 minutes; the time shown is the time of the quotes. They are not dealing prices: you buy at the offer and sell at the bid. A gilt with no two-way quote shows its last price instead. Outside trading hours each gilt shows the last mid price of the previous session (or, if there was none, its last trade). Every price is checked against that gilt's previous closing price (from YieldSmart's own daily record) and rejected if it is more than 10% away — a gilt that fails, or that the LSE doesn't list, shows its last closing price instead; the date the prices are from is shown on every page. Always check the live price with your broker before dealing.
Instrument details — each gilt's coupon, maturity date, coupon dates, first issue date and ISIN — come from the UK Debt Management Office's register of gilts in issue, checked for changes every day. Yields, net yields and durations are recalculated from the latest price.
Price history charts (on every gilt page: the last month free, up to 5 years with Premium) use daily closing prices (YieldSmart's own record of London Stock Exchange closes, plus five years of end-of-day history from our data provider), with each day's yields recalculated from that day's price. The 5-year view shows one close per week; shorter views show every trading day. The latest point on a chart is today's price, labelled as such. A few recently issued gilts start their history from when we began recording them.
The historical yield curve uses the Bank of England's estimated nominal spot-rate curve, published daily. These are zero-coupon spot rates, which differ from redemption (par) yields, most visibly at the long end. Contains public sector information licensed under the Open Government Licence v3.0.
The headline gross yield is the conventional gross redemption yield (yield to maturity), before tax. Our net yield is the internal rate of return (IRR) of the gilt's after-tax cash flows, held to maturity:
We discount on exactly the same basis as the gross yield — actual coupon dates, T+1 settlement, the dirty price and the fractional period to the next coupon — so at 0% tax the net yield equals the gross yield.
This is why a low-coupon gilt trading below par shows a higher net yield for higher-rate taxpayers — most of its return is the tax-free pull to par rather than taxable coupon.
The Savings Rate Equivalent is the gross yield a fully-taxable investment (a savings account, an at-par bond) would need to pay to match the gilt's net yield, at your tax rate. Savings interest is taxed at the same rates — including the 2-point rise from 6 April 2027 — so we use your rate averaged over the gilt's remaining life (time-weighted between today's rate and the post-April-2027 rate):
It is the fair, like-for-like comparator against a savings rate or deposit.
On the gilt table you can say when you need the money. We then rank the conventional gilts by their after-tax return to that date, as a yield a year (on the same basis as the net yield):
Coupons are taxed at your band (rising by 2 points from 6 April 2027), with the Accrued Income Scheme on the first coupon and on any sale; the gain to £100 or on a sale is CGT-free. Index-linked gilts aren’t ranked, because their cash depends on future inflation.
Yield scatter: today's dots use today's prices, exactly as the gilt table. The comparison dots use each gilt's closing price on the chosen date (or the last close before it, if that was a weekend or holiday), with the yield worked out as of that date — so the years to maturity, the next coupon and, for net yield, the tax rate on each coupon are all as they were then. Duration is Macaulay duration on the same cashflows. Past dates include the conventional gilts repaid since then (from the DMO's list of redeemed gilts, with their closing prices up to the day before repayment), so the short end looks as it did on that date; index-linked gilts repaid since aren't included. The same repaid gilts fill the short end of the actual-gilts curve-steepness chart. The optional Bank of England line is its fitted nominal spot curve at 2, 5, 7, 10 and 30 years — a smoothed, before-tax reference, not a gilt you can buy. Index-linked gilts show real yield for the 3-month-lag gilts; the two older 8-month-lag gilts are left out.
Compare gilts uses the same daily closes and per-day yields as the price history on each gilt page; with two gilts, the gap is the first minus the second on each day (basis points for yields, £ per £100 for price) or the first divided by the second. Curve steepness is the difference between two maturities (10y−2y, 30y−10y, 5y−2y, 10y−5y or 30y−2y), one reading a week, measured either on the Bank of England's nominal spot curve or from the actual gilts: for each maturity, the yield is interpolated between the two conventional gilts either side of it from that week's closing prices, gross or after tax at 20/40/45%. Where the nearest gilts either side are far apart (some older short-maturity readings, whose gilts have since been repaid), no reading is shown. Gilts vs cash compares a gilt's yield to maturity on each day, before and after income tax, with the top-paying instant-access savings account at the time, before and after the same tax — instant access because a gilt can be sold on any business day, so cash you can only withdraw a few times a year isn't a like-for-like comparison. No free historical series of best-buy rates exists, so we record, from each monthly snapshot of MoneySavingExpert's savings guide (via the Internet Archive, from September 2021), the top account in its main easy-access table that allows unlimited penalty-free withdrawals; is ordinary taxable savings (not a cash ISA) open to anyone; has no balance cap under £10,000 and no minimum deposit over £10,000; and needs no paid account, monthly pay-in or existing relationship — a saver that comes with a free current account you open just to get it (as Chase's does) counts. An account whose rate drops, or that charges, after a few withdrawals doesn't qualify. A 12-month introductory bonus counts, because a saver switching that month received it. Months with no archived snapshot carry the previous month's rate forward. (Until 31 October 2026 this line used a looser rule — at least about four withdrawals a year — and was re-checked month by month when the rule changed.) Bank Rate (IUDBEDR) is shown before tax for reference, and the Bank of England's average rate across all instant-access accounts (IUMB6VJ) can be added. Neither side includes your Personal Savings Allowance.
In the gilt table's deal ticket (the Deal ticket button in a gilt's detail panel), members can type the price their platform quotes them — the offer when buying, the bid when selling — plus their commission (a fixed £, a % of the deal, or both, with an optional minimum and maximum) and platform fee. Fees are saved to the account; quoted prices are not. Index-linked gilts aren't covered. Amounts can be entered as cash or as nominal on either side: buying £X nominal costs nominal × (offer + accrued) ÷ 100 before commission; selling to raise £X finds the smallest nominal (to the penny) whose proceeds after commission are at least £X.
The ticket builds the deal the way a dealing ticket does: nominal × clean price = principal, plus accrued interest (with the number of days and the period it covers, actual/actual), = consideration, then commission and stamp duty (nil — gilts are exempt) to the total you pay or receive. An order placed at a weekend or on a bank holiday trades on the next business day and settles the business day after (T+1).
Buying: the cash you enter buys nominal at the offer plus accrued interest; commission is paid on top. The yield after costs is the gross and net yield to maturity on the all-in price — what you paid including commission, spread over the nominal bought — on the same cashflow timeline as every other yield (actual coupon dates, the Accrued Income Scheme on the first coupon, the higher rates from 6 April 2027). A one-off commission therefore costs far more yield on a short gilt than a long one. A platform fee (a % a year, optionally capped, or a flat £ a year) is then taken off as a straight yearly percentage of the cash invested; it isn't tax-deductible, so it comes off gross and net alike. If your account already pays its cap or a flat fee, buying a gilt adds nothing and the fee should be left at 0. When you type an offer, the panel also shows what buying at the mid would have yielded, i.e. what the bid-offer spread costs.
Selling: proceeds are the nominal × the bid, plus the accrued interest the buyer pays you (negative if the sale settles ex-dividend, when you keep the next coupon), less commission. Under the Accrued Income Scheme — which applies if your gilts and other bonds came to more than £5,000 nominal at any time in the tax year or the one before — that accrued interest is taxed as income at your band (the rate in force on the next coupon date, when the charge arises); an ex-dividend sale gives relief instead. Any unused Personal Savings Allowance isn't applied here. If you enter what you paid (or hold the gilt in your portfolio), the price gain is shown: it is free of CGT, and a loss can't be set against other gains. Coupons already received and platform fees aren't counted on a sale.
When you buy a gilt between coupon dates you also pay the interest that has built up since the last coupon (the difference between the clean price quoted and the dirty price you settle). We calculate accrued interest to a T+1 settlement date on an actual/actual day-count basis — actual days since the last coupon divided by the actual days in the coupon period, in UTC.
T+1 skips weekends and UK bank holidays. Inside the ex-dividend period (the 7 business days before a coupon) accrued interest is negative: the seller keeps the coming coupon, so you pay less than the clean price.
Newly issued gilts. A gilt's first coupon only pays for the days from its first issue date, so it is usually short (for example the 4⅝% Treasury Gilt 2030, issued 11 September 2026, pays £0.904891 per £100 on 22 November 2026 rather than the usual £2.3125). Until that first coupon is paid, accrued interest runs from the issue date and the first coupon is the reduced amount, as the DMO publishes it.
Modified duration measures price sensitivity to yields: roughly, the percentage change in price for a 1% change in yield. We use the standard semi-annual formula — Macaulay duration on the gilt's actual remaining cash flows (real coupon dates, the fractional period to the next coupon), discounted at the gross yield, divided by (1 + y/2):
Longer-dated gilts have higher duration and so larger price swings when interest rates move — the main risk for a gilt held and sold before maturity.
We apply current UK tax rules as they affect a private individual holding gilts directly (not through a fund or wrapper):
Inside an ISA or SIPP there is no income tax on coupons, so the after-tax yield is simply the gross yield. Compare gilts and the Ladder builder let you choose General account, ISA or SIPP; everywhere else assumes a general (taxable) account.
For index-linked gilts with a 3-month indexation lag (all issued since 2005) we show the real yield — the inflation-adjusted yield, computed from the quoted real price with no inflation assumption — and break-even inflation: the yield of a conventional gilt of the same maturity (interpolated along the curve) minus the real yield. If RPI inflation averages more than the break-even, the index-linked gilt does better. The two older 8-month-lag gilts (2030 and 2035) can only be given a real yield by assuming future inflation, which we show alongside (2%). The inflation uplift on the principal is CGT-free; the coupon (including its inflation uplift) is taxable income.
YieldSmart is an independent tool built to make institutional-grade after-tax gilt analysis available to retail investors.
Information only — not financial advice. Gilt prices are indicative from last available close and may be delayed. Verify before transacting. UK tax treatment depends on your circumstances and may change.