diff --git a/frontend/src/pages/Tariffs.tsx b/frontend/src/pages/Tariffs.tsx
index f6acf65..a583ab0 100644
--- a/frontend/src/pages/Tariffs.tsx
+++ b/frontend/src/pages/Tariffs.tsx
@@ -109,13 +109,14 @@ export default function Tariffs() {
         ? Object.fromEntries(form.windows.map(w => [w.label.toLowerCase(), w.split_pct]))
         : {}
       const windows = form.windows.map(({ split_pct: _split_pct, ...w }) => w)
+      const isElectric = categories.find(c => c.id === form.category_id)?.key === 'electric'
       const body = {
         category_id: form.category_id, name: form.name.trim(), supplier: form.supplier || null,
         effective_from: form.effective_from, effective_to: form.effective_to || null,
         standing_charge_pence_per_day: form.standing_charge_pence_per_day,
         ccl_rate_pence_per_unit: form.ccl_rate_pence_per_unit === '' ? null : form.ccl_rate_pence_per_unit,
         ccl_exempt: form.ccl_exempt,
-        rab_levy_rate_pence_per_unit: form.rab_levy_rate_pence_per_unit === '' ? null : form.rab_levy_rate_pence_per_unit,
+        rab_levy_rate_pence_per_unit: !isElectric || form.rab_levy_rate_pence_per_unit === '' ? null : form.rab_levy_rate_pence_per_unit,
         metering_charge_pence_per_month: form.metering_charge_pence_per_month,
         other_charges_pence_per_month: form.other_charges_pence_per_month,
         vat_rate_pct: form.vat_rate_pct, is_time_of_use: form.is_time_of_use,
@@ -195,7 +196,12 @@ export default function Tariffs() {
               </div>
               <div className="field">
                 <label>Category</label>
-                <select value={form.category_id} onChange={e => setForm({ ...form, category_id: parseInt(e.target.value) })}>
+                <select value={form.category_id} onChange={e => {
+                  const category_id = parseInt(e.target.value)
+                  const category = categories.find(c => c.id === category_id)
+                  const clearRabLevy = category?.key !== 'electric'
+                  setForm({ ...form, category_id, rab_levy_rate_pence_per_unit: clearRabLevy ? '' : form.rab_levy_rate_pence_per_unit })
+                }}>
                   {categories.map(c => <option key={c.id} value={c.id}>{c.name}</option>)}
                 </select>
               </div>
@@ -238,11 +244,13 @@ export default function Tariffs() {
             </label>
 
             <div className="field-row">
-              <div className="field">
-                <label>Nuclear RAB levy (pence/unit)</label>
-                <input type="number" step="0.0001" value={form.rab_levy_rate_pence_per_unit}
-                  onChange={e => setForm({ ...form, rab_levy_rate_pence_per_unit: e.target.value === '' ? '' : parseFloat(e.target.value) })} />
-              </div>
+              {categories.find(c => c.id === form.category_id)?.key === 'electric' && (
+                <div className="field">
+                  <label>Nuclear RAB levy (pence/unit)</label>
+                  <input type="number" step="0.0001" value={form.rab_levy_rate_pence_per_unit}
+                    onChange={e => setForm({ ...form, rab_levy_rate_pence_per_unit: e.target.value === '' ? '' : parseFloat(e.target.value) })} />
+                </div>
+              )}
               <div className="field">
                 <label>Metering charge (£/month)</label>
                 <input type="number" step="0.01" value={form.metering_charge_pence_per_month / 100}