Signature
T = max(5, Q_3 + 1.5 * (Q_3 - Q_1)); X = max(0, L_a - T)
| Inputs | Definition | Unit |
|---|---|---|
Q_3 | Third quartile of adjusted length of stay for spells in the HRG | days |
Q_1 | First quartile of adjusted length of stay for spells in the HRG | days |
L_a | Number of changes of calendar day from admission to discharge, after deducting days in critical care, rehabilitation, specialist palliative care and delayed transfers of care | days |
T | Trim point for the spell HRG, rounded to the nearest whole number | days |
|---|---|---|
X | Days of the spell above the trim point, zero when the spell does not exceed it | days |
Function
Average length of stay calculation and bed-day costing function
Maps the bed-days and discharges of a period to the average length of stay (ALOS), and relates length of stay to bed capacity, payment trim points, a case-mix adjusted comparison and the cost of an admission or of a change in stay. The records follow the notation of the Average Length of Stay article, where L_bar is the average stay in days and N the number of discharges.
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Implementations
Excel
Trim point and excess bed days in two cells
The first formula returns the rounded trim point from named cells for the lower and upper quartiles; the second returns the excess bed days of a spell from its adjusted length of stay and the trim point cell.
=ROUND(MAX(5,UpperQuartileLOS+1.5*(UpperQuartileLOS-LowerQuartileLOS)),0); =MAX(0,AdjLOS-TrimPoint)
Assumptions
Adjusted length of stay as the basis for trim points
The quartiles and each spell's length of stay use the adjusted length of stay, so a same-day spell counts as zero days and the deducted days are funded elsewhere.
Quartiles from the spells of one HRG
Q_1 and Q_3 come from the spells grouped to the same spell HRG in the reference data. The quartile method is not fixed by the formula, so the one used is stated.
Worked examples
Trim point from quartiles of 2 and 6 days
Illustrative quartiles of 2 and 6 days give a trim point of 6 plus 1.5 times 4, which is 12 days. A spell with an adjusted length of stay of 15 days has 3 excess bed days.
Q_1 = 2; Q_3 = 6; L_a = 15; T = 12; X = 3
Short-stay HRG held at the 5-day floor
Illustrative quartiles of 1 and 2 days give 3.5 days, below the floor, so the trim point is 5 days. A 4-day spell has no excess bed days.
Q_1 = 1; Q_3 = 2; L_a = 4; T = 5; X = 0
Common errors
Excess bed days without the zero floor
Computing excess bed days as length of stay minus trim point without the zero floor gives negative values for short spells: a 4-day spell against a 12-day trim point would subtract 8 days from the HRG total and understate long-stay funding.
Trim points from unadjusted length of stay
Using raw spell length, including critical care, rehabilitation, specialist palliative care and delayed transfer days, raises both the quartiles and each spell's stay, so excess bed days no longer match the Payment Scheme rule.
Sources
NHS Payment Scheme trim point and excess bed day rule
NHS England. 2025/26 NHS Payment Scheme, Annex D: Prices and cost adjustments. 2025, updated June 2025. Appendix 1 gives the spell HRG trim point formula, rounded to the nearest whole number, the definition of adjusted length of stay and the excess bed day rule; Appendix 3 describes the daily long-stay payment.
Canonical Identity
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