The clean price on a gilt row is a stored close from a named source, and the gross yield beside it is computed from that price rather than quoted independently, which is why the two agree by construction.
Every page names the report it was built from
The conventional gilts list, the gilt yield curve and the gilt's own history are all built from a stored daily report, and each says which report date it was built from. That date is the anchor for every figure on the page: a clean price, an accrued amount and a yield all describe the same settlement on the same market day. When a page shows no report, it shows an empty state rather than a stale price, because there is nothing to date the numbers with.
Within that report, each row carries its own provenance — which feed priced the row, the price date, the settlement the figures were derived on, and the basis the accrued interest came from. A row priced from a market data provider's close is not the same quote as one priced from the Debt Management Office's dealer report, and the provenance is what lets the two be told apart after the fact. The record behind that sentence also holds the storage path and the calculation version, which stay in the ledger for an audit rather than on the page.
The two-sided quote behind the mid price
The Debt Management Office publishes a purchase and sale prices report, known as D10B, which quotes four prices for every gilt in issue: the price at which it will buy and the price at which it will sell, each quoted both clean and dirty. The report is a dealer quote rather than a single traded price, and the mid that a list displays is the midpoint of the two-sided quote — the figure between the bid and the offer, before the width of the spread is applied in either direction.
The dirty prices in the same report embed an accrual for the value date the DMO deals on, which is not necessarily the settlement a reader's own trade will use. That is why the site computes its own accrued interest from the gilt's coupon schedule rather than reading it off the D10B pair: the published dirty price is a correct figure for the DMO's own value date, and a different settlement needs a different one.
The yield is computed from the price
The gross yield on a row is not an independent quote. It is the rate at which the gilt's remaining cash flows discount back to the price the report stored, and the site's NPV column states the identity from the other direction: discount every remaining coupon and the final repayment at the gross redemption yield, add them up, and the total is the dirty price per £100 nominal. A stored close and the mid its own yield implies are therefore the same figure read two ways.
That equality is a property of the calculation, not a coincidence that happens to hold on a good day. It also means the interesting question is not whether the price and the yield agree, but which price the yield was computed from. Two rows can show a gap between a stored close and the price implied by a yield only when the two figures came from different sources or different dates, and the provenance on the row is what settles which.
The site does not publish a separate recomputation of the DMO's own report figure. It stores a price from a named source, computes its own accrued and yields from that price and the gilt's schedule, and records the calculation version the arithmetic was done under.
Why two prices for the same gilt differ
A market data provider publishes a single closing clean price for a gilt, not a two-sided dealer quote. The provider's close and the DMO mid are both honest prices for the same gilt on the same day, and they can differ by roughly the width of the dealer's spread, with the mid sitting above a single close. The two legs are the DMO's D10B report and the provider's closing prices, and the gap between them is a level difference rather than a market move.
A level difference of that kind is not a market move, and the two series must never be differenced against each other: subtracting one from the other on two dates would report a price change that no gilt experienced. The curve page is built from the provider's closes so that a fit can be compared against an external gilt reference on like terms; the list's rows record which feed priced them, so a reader can see whether a row and the curve are on the same level before comparing them.
| Source | What it publishes | How the site uses it |
| DMO D10B | Purchase and sale prices, clean and dirty, per gilt | The dealer quote a mid is taken from |
| Market data provider | A single closing clean price per gilt | A closing reference, and the basis of the curve |
| Both | The same gilt on the same day | Recorded per row as provenance, never blended |
The reference yield is a different convention
A provider also publishes its own reference yield, and that figure is on a semi-annual compounding convention. The site's headline gross yield compounds once a year. The two differ by roughly the square of the yield divided by four, which is a few basis points at ordinary levels — the direction and size are the same as the gap between the gross and DMO columns. A reference yield compared raw against the annual gross yield would therefore show a basis error rather than a disagreement about the gilt.
Reading a row therefore means reading its labels. The gross yield is the site's annual figure computed from the stored price; the DMO yield is the market-convention version of the same quantity; and any externally published reference yield is a third figure on its own convention. They are three measurements of one gilt, and none of them is wrong — they are answers to slightly different questions.
Background, not advice
This article explains where the price on a gilt row comes from and how it relates to the yield beside it; it is general background, not investment, tax or legal advice for any reader's circumstances. Prices move, and a stored close describes one day rather than the next. The Debt Management Office, the market data provider and the report date printed on the page are the primary sources for a real price, and the provenance shown on the row records which of them was used.