diff --git a/backend/src/lib/cost-calc.js b/backend/src/lib/cost-calc.js
index 08bce82..d23d6ec 100644
--- a/backend/src/lib/cost-calc.js
+++ b/backend/src/lib/cost-calc.js
@@ -105,6 +105,25 @@ async function interpolatedValueAtDate(meterId, date) {
   return { value, before, after }
 }
 
+// Classifies how a period's consumption figure was actually derived, for
+// display next to a report row:
+// - 'no_data'     — no readings cover the period at all
+// - 'partial'     — real data only reaches as_of_date, short of periodEnd
+//                   (the normal case for a still-open current period)
+// - 'complete'    — readings land exactly on both boundaries, no interpolation
+//                   needed — either a lucky manual coincidence or, once a
+//                   device feeds daily readings, the normal case
+// - 'distributed' — full period covered, but one or both boundaries needed
+//                   interpolating across a sparse-reading gap
+function classifyBasis(hasData, periodStart, periodEnd, first, last) {
+  if (!hasData) return { status: 'no_data', as_of_date: null }
+  const lastDate = toISODate(last.reading_date)
+  if (lastDate < periodEnd) return { status: 'partial', as_of_date: lastDate }
+  const firstDate = toISODate(first.reading_date)
+  if (firstDate === periodStart && lastDate === periodEnd) return { status: 'complete', as_of_date: null }
+  return { status: 'distributed', as_of_date: null }
+}
+
 // Consumption for a meter over [periodStart, periodEnd] (inclusive). Interpolates
 // the meter's value at each boundary between the real readings bracketing it,
 // then takes the difference — so a period's consumption is prorated by days
@@ -119,17 +138,21 @@ export async function getPeriodConsumption(meterId, periodStart, periodEnd) {
   if (!startPoint || !endPoint) {
     const first = (await readingOnOrAfter(meterId, periodStart)) || (await readingOnOrBefore(meterId, periodStart))
     const last = await readingOnOrBefore(meterId, periodEnd)
-    if (!first || !last || last.reading_date <= first.reading_date) {
-      return { consumption: null, first, last, has_data: false }
+    const hasData = !!(first && last && last.reading_date > first.reading_date)
+    const basis = classifyBasis(hasData, periodStart, periodEnd, first, last)
+    if (!hasData) {
+      return { consumption: null, first, last, has_data: false, ...basis }
     }
     const rawConsumption = Number(last.reading_value) - Number(first.reading_value)
     const consumption = await convertMeterConsumption(meterId, rawConsumption)
-    return { consumption, first, last, has_data: true }
+    return { consumption, first, last, has_data: true, ...basis }
   }
 
+  const first = startPoint.before
+  const last = endPoint.after
   const rawConsumption = endPoint.value - startPoint.value
   const consumption = await convertMeterConsumption(meterId, rawConsumption)
-  return { consumption, first: startPoint.before, last: endPoint.after, has_data: true }
+  return { consumption, first, last, has_data: true, ...classifyBasis(true, periodStart, periodEnd, first, last) }
 }
 
 // Trailing average daily consumption as of the meter's latest reading,
@@ -391,10 +414,13 @@ async function splitCostAcrossSegments(meterId, rangeStart, rangeEnd, consumptio
 // or backdated after the fact) that falls inside the period. `asOfDate` is only
 // used as a fallback when the meter has no tariff-assignment history at all.
 export async function getMeterCostForPeriod(meterId, periodStart, periodEnd, asOfDate) {
-  const { consumption, first, last, has_data } = await getPeriodConsumption(meterId, periodStart, periodEnd)
+  const { consumption, first, last, has_data, status, as_of_date } = await getPeriodConsumption(meterId, periodStart, periodEnd)
   const daysInPeriod = daysInclusive(periodStart, periodEnd)
   const costed = await splitCostAcrossSegments(meterId, periodStart, periodEnd, consumption, asOfDate || periodEnd)
-  return { consumption, has_data, first_reading: first, last_reading: last, days_in_period: daysInPeriod, ...costed }
+  return {
+    consumption, has_data, status, as_of_date,
+    first_reading: first, last_reading: last, days_in_period: daysInPeriod, ...costed,
+  }
 }
 
 // Estimate for the remainder of an open period: actual consumption to date +
diff --git a/frontend/src/index.css b/frontend/src/index.css
index a082dc2..02293ca 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -344,6 +344,7 @@ table.data tr.clickable { cursor: pointer; }
 table.data tr.clickable:hover td { background: var(--body-bg); }
 table.data td.num { text-align: right; font-variant-numeric: tabular-nums; }
 table.data tr.total-row td { font-weight: 700; background: var(--body-bg); border-top: 2px solid var(--card-border); }
+table.data tr.subtotal-row td { font-weight: 600; background: var(--body-bg); border-top: 1px solid var(--card-border); }
 table.data tr.anomaly-row td { background: var(--danger-bg); }
 
 /* ── Stats strip ───────────────────────────────────────────── */
diff --git a/frontend/src/pages/Estimates.tsx b/frontend/src/pages/Estimates.tsx
index 3da9b02..e775079 100644
--- a/frontend/src/pages/Estimates.tsx
+++ b/frontend/src/pages/Estimates.tsx
@@ -1,11 +1,18 @@
-import { useCallback, useEffect, useState } from 'react'
+import { Fragment, useCallback, useEffect, useState } from 'react'
 import { useAuth } from '../components/AuthGate'
-import { can, formatMoney, formatUnits } from '../types'
-import type { Category, EstimateReport } from '../types'
+import { can, formatMoney, formatUnits, groupByCategory } from '../types'
+import type { Category, EstimateReport, EstimateRow } from '../types'
 import * as api from '../api'
 
 const WINDOW_OPTIONS = [7, 14, 30]
 
+function sumEstimateCosts(rows: EstimateRow[]) {
+  return rows.reduce((acc, r) => ({
+    projected_consumption: acc.projected_consumption + (r.projected_consumption || 0),
+    total_pence: acc.total_pence + r.total_pence,
+  }), { projected_consumption: 0, total_pence: 0 })
+}
+
 export default function Estimates() {
   const { user } = useAuth()
   const canEdit = can(user, 'estimates')
@@ -84,25 +91,37 @@ export default function Estimates() {
               <table className="data">
                 <thead>
                   <tr>
-                    <th>Meter</th><th>Category</th><th className="num">Trailing window</th>
+                    <th>Meter</th><th className="num">Trailing window</th>
                     <th className="num">Daily rate</th><th className="num">Actual to date</th>
                     <th className="num">Remaining days</th><th className="num">Projected consumption</th>
                     <th className="num">Projected cost</th>
                   </tr>
                 </thead>
                 <tbody>
-                  {report.meters.map(m => (
-                    <tr key={m.meter_id}>
-                      <td>{m.meter_name}</td>
-                      <td>{m.category_name}</td>
-                      <td className="num">{m.trailing_window_days}d</td>
-                      <td className="num">{m.daily_rate != null ? formatUnits(m.daily_rate, `${m.unit_label}/day`) : '—'}</td>
-                      <td className="num">{formatUnits(m.actual_to_date, m.unit_label)}</td>
-                      <td className="num">{m.remaining_days}</td>
-                      <td className="num">{formatUnits(m.projected_consumption, m.unit_label)}</td>
-                      <td className="num">{formatMoney(m.total_pence)}</td>
-                    </tr>
-                  ))}
+                  {groupByCategory(report.meters).map(group => {
+                    const subtotal = sumEstimateCosts(group.rows)
+                    return (
+                      <Fragment key={group.category_id}>
+                        {group.rows.map(m => (
+                          <tr key={m.meter_id}>
+                            <td>{m.meter_name}</td>
+                            <td className="num">{m.trailing_window_days}d</td>
+                            <td className="num">{m.daily_rate != null ? formatUnits(m.daily_rate, `${m.unit_label}/day`) : '—'}</td>
+                            <td className="num">{formatUnits(m.actual_to_date, m.unit_label)}</td>
+                            <td className="num">{m.remaining_days}</td>
+                            <td className="num">{formatUnits(m.projected_consumption, m.unit_label)}</td>
+                            <td className="num">{formatMoney(m.total_pence)}</td>
+                          </tr>
+                        ))}
+                        <tr className="subtotal-row">
+                          <td>{group.category_name} subtotal</td>
+                          <td></td><td></td><td></td><td></td>
+                          <td className="num">{formatUnits(subtotal.projected_consumption, group.unit_label)}</td>
+                          <td className="num">{formatMoney(subtotal.total_pence)}</td>
+                        </tr>
+                      </Fragment>
+                    )
+                  })}
                 </tbody>
               </table>
             </div>
diff --git a/frontend/src/pages/Reports.tsx b/frontend/src/pages/Reports.tsx
index d61e1aa..a2ecd25 100644
--- a/frontend/src/pages/Reports.tsx
+++ b/frontend/src/pages/Reports.tsx
@@ -1,9 +1,24 @@
-import { useCallback, useEffect, useState } from 'react'
+import { Fragment, useCallback, useEffect, useState } from 'react'
 import { AlertTriangle } from 'lucide-react'
-import { formatMoney, formatUnits } from '../types'
-import type { Category, ConsumptionCostReport, RollupReport } from '../types'
+import { formatMoney, formatUnits, groupByCategory, formatBasis } from '../types'
+import type { Category, ConsumptionCostReport, RollupReport, MeterCostRow } from '../types'
 import * as api from '../api'
 
+function extrasFor(m: { ccl_cost_pence: number; rab_levy_cost_pence: number; metering_cost_pence: number; other_charges_cost_pence: number }): number {
+  return m.ccl_cost_pence + m.rab_levy_cost_pence + m.metering_cost_pence + m.other_charges_cost_pence
+}
+
+function sumMeterCosts(rows: MeterCostRow[]) {
+  return rows.reduce((acc, r) => ({
+    consumption: acc.consumption + (r.consumption || 0),
+    usage_cost_pence: acc.usage_cost_pence + r.usage_cost_pence,
+    standing_cost_pence: acc.standing_cost_pence + r.standing_cost_pence,
+    extras_cost_pence: acc.extras_cost_pence + extrasFor(r),
+    vat_pence: acc.vat_pence + r.vat_pence,
+    total_pence: acc.total_pence + r.total_pence,
+  }), { consumption: 0, usage_cost_pence: 0, standing_cost_pence: 0, extras_cost_pence: 0, vat_pence: 0, total_pence: 0 })
+}
+
 function currentPeriod(): string {
   const now = new Date()
   return `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}`
@@ -56,9 +71,7 @@ export default function Reports() {
             <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.total_pence)}</div><div className="stat-label">Total cost</div></div>
             <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.usage_cost_pence)}</div><div className="stat-label">Usage</div></div>
             <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.standing_cost_pence)}</div><div className="stat-label">Standing</div></div>
-            <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.ccl_cost_pence)}</div><div className="stat-label">CCL</div></div>
-            <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.rab_levy_cost_pence)}</div><div className="stat-label">RAB Levy</div></div>
-            <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.metering_cost_pence + report.totals.other_charges_cost_pence)}</div><div className="stat-label">Fixed extras</div></div>
+            <div className="stat-box"><div className="stat-value">{formatMoney(extrasFor(report.totals))}</div><div className="stat-label">Extras</div></div>
             <div className="stat-box"><div className="stat-value">{formatMoney(report.totals.vat_pence)}</div><div className="stat-label">VAT</div></div>
           </div>
 
@@ -70,45 +83,57 @@ export default function Reports() {
               <table className="data">
                 <thead>
                   <tr>
-                    <th>Meter</th><th>Category</th><th className="num">Consumption</th>
-                    <th className="num">Usage</th><th className="num">Standing</th><th className="num">CCL</th>
-                    <th className="num">RAB Levy</th><th className="num">Fixed extras</th>
-                    <th className="num">VAT</th><th className="num">Total</th>
+                    <th>Meter</th><th className="num">Consumption</th>
+                    <th className="num">Usage</th><th className="num">Standing</th><th className="num">Extras</th>
+                    <th className="num">VAT</th><th className="num">Total</th><th>Basis</th>
                   </tr>
                 </thead>
                 <tbody>
-                  {report.meters.map(m => (
-                    <tr key={m.meter_id}>
-                      <td>
-                        {m.meter_name}
-                        {!m.has_data && <span className="badge badge-outline" style={{ marginLeft: 6 }}>no data</span>}
-                        {m.rate_changed_mid_period && (
-                          <span className="badge badge-tou" style={{ marginLeft: 6 }} title={m.segments.map(s => `${s.tariff_name}: ${s.seg_start} – ${s.seg_end}`).join(', ')}>
-                            rate changed
-                          </span>
-                        )}
-                      </td>
-                      <td>{m.category_name}</td>
-                      <td className="num">{formatUnits(m.consumption, m.unit_label)}</td>
-                      <td className="num">{formatMoney(m.usage_cost_pence)}</td>
-                      <td className="num">{formatMoney(m.standing_cost_pence)}</td>
-                      <td className="num">{formatMoney(m.ccl_cost_pence)}</td>
-                      <td className="num">{formatMoney(m.rab_levy_cost_pence)}</td>
-                      <td className="num">{formatMoney(m.metering_cost_pence + m.other_charges_cost_pence)}</td>
-                      <td className="num">{formatMoney(m.vat_pence)}</td>
-                      <td className="num">{formatMoney(m.total_pence)}</td>
-                    </tr>
-                  ))}
+                  {groupByCategory(report.meters).map(group => {
+                    const subtotal = sumMeterCosts(group.rows)
+                    return (
+                      <Fragment key={group.category_id}>
+                        {group.rows.map(m => (
+                          <tr key={m.meter_id}>
+                            <td>
+                              {m.meter_name}
+                              {m.rate_changed_mid_period && (
+                                <span className="badge badge-tou" style={{ marginLeft: 6 }} title={m.segments.map(s => `${s.tariff_name}: ${s.seg_start} – ${s.seg_end}`).join(', ')}>
+                                  rate changed
+                                </span>
+                              )}
+                            </td>
+                            <td className="num">{formatUnits(m.consumption, m.unit_label)}</td>
+                            <td className="num">{formatMoney(m.usage_cost_pence)}</td>
+                            <td className="num">{formatMoney(m.standing_cost_pence)}</td>
+                            <td className="num">{formatMoney(extrasFor(m))}</td>
+                            <td className="num">{formatMoney(m.vat_pence)}</td>
+                            <td className="num">{formatMoney(m.total_pence)}</td>
+                            <td>{formatBasis(m.status, m.as_of_date)}</td>
+                          </tr>
+                        ))}
+                        <tr className="subtotal-row">
+                          <td>{group.category_name} subtotal</td>
+                          <td className="num">{formatUnits(subtotal.consumption, group.unit_label)}</td>
+                          <td className="num">{formatMoney(subtotal.usage_cost_pence)}</td>
+                          <td className="num">{formatMoney(subtotal.standing_cost_pence)}</td>
+                          <td className="num">{formatMoney(subtotal.extras_cost_pence)}</td>
+                          <td className="num">{formatMoney(subtotal.vat_pence)}</td>
+                          <td className="num">{formatMoney(subtotal.total_pence)}</td>
+                          <td></td>
+                        </tr>
+                      </Fragment>
+                    )
+                  })}
                   <tr className="total-row">
-                    <td colSpan={2}>Total</td>
-                    <td className="num">{report.totals.consumption.toLocaleString(undefined, { maximumFractionDigits: 1 })}</td>
+                    <td>Total</td>
+                    <td className="num" title="Not summed — mixes units across fuel types">—</td>
                     <td className="num">{formatMoney(report.totals.usage_cost_pence)}</td>
                     <td className="num">{formatMoney(report.totals.standing_cost_pence)}</td>
-                    <td className="num">{formatMoney(report.totals.ccl_cost_pence)}</td>
-                    <td className="num">{formatMoney(report.totals.rab_levy_cost_pence)}</td>
-                    <td className="num">{formatMoney(report.totals.metering_cost_pence + report.totals.other_charges_cost_pence)}</td>
+                    <td className="num">{formatMoney(extrasFor(report.totals))}</td>
                     <td className="num">{formatMoney(report.totals.vat_pence)}</td>
                     <td className="num">{formatMoney(report.totals.total_pence)}</td>
+                    <td></td>
                   </tr>
                 </tbody>
               </table>
diff --git a/frontend/src/types.ts b/frontend/src/types.ts
index 98225e1..e344f48 100644
--- a/frontend/src/types.ts
+++ b/frontend/src/types.ts
@@ -156,6 +156,11 @@ export interface CostBreakdown {
   rate_changed_mid_period: boolean
 }
 
+// How a period's consumption figure was actually derived — see cost-calc.js's
+// classifyBasis(). 'partial' covers the normal "still-open current period"
+// case; as_of_date is only set then.
+export type ConsumptionBasis = 'no_data' | 'partial' | 'complete' | 'distributed'
+
 export interface MeterCostRow extends CostBreakdown {
   meter_id: number
   meter_name: string
@@ -164,10 +169,39 @@ export interface MeterCostRow extends CostBreakdown {
   unit_label: string
   consumption: number | null
   has_data: boolean
+  status: ConsumptionBasis
+  as_of_date: string | null
   days_in_period: number
   tariff: Tariff | null
 }
 
+// Groups rows sharing a category_id together, preserving first-seen order
+// (meters already arrive sorted by category from the backend).
+export function groupByCategory<T extends { category_id: number; category_name: string; unit_label: string }>(
+  rows: T[]
+): { category_id: number; category_name: string; unit_label: string; rows: T[] }[] {
+  const order: number[] = []
+  const map = new Map<number, { category_id: number; category_name: string; unit_label: string; rows: T[] }>()
+  for (const r of rows) {
+    if (!map.has(r.category_id)) {
+      order.push(r.category_id)
+      map.set(r.category_id, { category_id: r.category_id, category_name: r.category_name, unit_label: r.unit_label, rows: [] })
+    }
+    map.get(r.category_id)!.rows.push(r)
+  }
+  return order.map(id => map.get(id)!)
+}
+
+// "Complete/Distributed/Up to date/As of [date]/No data" — see ConsumptionBasis.
+export function formatBasis(status: ConsumptionBasis, asOfDate: string | null): string {
+  if (status === 'no_data') return 'No data'
+  if (status === 'complete') return 'Complete'
+  if (status === 'distributed') return 'Distributed'
+  const today = new Date().toISOString().slice(0, 10)
+  if (asOfDate === today) return 'Up to date'
+  return asOfDate ? `As of ${new Date(asOfDate).toLocaleDateString('en-GB')}` : 'Partial'
+}
+
 export interface ConsumptionCostReport {
   period: { start: string; end: string; isCurrent: boolean }
   meters: MeterCostRow[]