diff --git a/apps/edr-freight-api/src/migrations/1900000000000-SimplifyRatesAndWeightLimitRules.ts b/apps/edr-freight-api/src/migrations/1900000000000-SimplifyRatesAndWeightLimitRules.ts
new file mode 100644
index 000000000..c03e70bbb
--- /dev/null
+++ b/apps/edr-freight-api/src/migrations/1900000000000-SimplifyRatesAndWeightLimitRules.ts
@@ -0,0 +1,121 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+/**
+ * Simplify the rate + weight-limit configuration model:
+ *
+ *  1. Drop the effective_from / effective_to validity window from both
+ *     `rates` and `weight_limit_rules`. Rates are now activated purely by
+ *     the approval workflow (status = LIVE) and weight limits are always
+ *     active for their container + direction. No time-travel scheduling.
+ *
+ *  2. Enforce "one rate per pattern" with partial unique indexes so the same
+ *     configuration (e.g. FIRST_MILE for a given container type) cannot be
+ *     duplicated. NULL scope columns are COALESCE-normalised because Postgres
+ *     treats NULLs as distinct in a plain unique index.
+ *
+ *  This migration is destructive on the date columns — existing effective_*
+ *  values are dropped.
+ */
+export class SimplifyRatesAndWeightLimitRules1900000000000 implements MigrationInterface {
+  name = 'SimplifyRatesAndWeightLimitRules1900000000000';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    // ── 1. De-duplicate existing data so the unique indexes can be created ──
+    // Keep the most recently-created row per pattern, soft-delete the rest.
+    await queryRunner.query(`
+      WITH ranked AS (
+        SELECT id,
+               row_number() OVER (
+                 PARTITION BY rate_type,
+                              COALESCE(container_type_id, '00000000-0000-0000-0000-000000000000'::uuid),
+                              COALESCE(cargo_type_id, '00000000-0000-0000-0000-000000000000'::uuid),
+                              COALESCE(trade_direction, '')
+                 ORDER BY created_at DESC, id DESC
+               ) AS rn
+        FROM freight.rates
+        WHERE deleted_at IS NULL AND status <> 'SUPERSEDED'
+      )
+      UPDATE freight.rates r
+      SET deleted_at = now()
+      FROM ranked
+      WHERE r.id = ranked.id AND ranked.rn > 1;
+    `);
+
+    await queryRunner.query(`
+      WITH ranked AS (
+        SELECT id,
+               row_number() OVER (
+                 PARTITION BY container_type_id, trade_direction
+                 ORDER BY created_at DESC, id DESC
+               ) AS rn
+        FROM freight.weight_limit_rules
+        WHERE deleted_at IS NULL
+      )
+      UPDATE freight.weight_limit_rules w
+      SET deleted_at = now()
+      FROM ranked
+      WHERE w.id = ranked.id AND ranked.rn > 1;
+    `);
+
+    // ── 2. Drop the effective-date indexes + columns ───────────────────────
+    await queryRunner.query(`DROP INDEX IF EXISTS freight."IDX_rates_effective_from";`);
+    await queryRunner.query(`DROP INDEX IF EXISTS freight."IDX_weight_limit_rules_effective_from";`);
+    // Indexes created by TypeORM's @Index carry generated hashed names — drop
+    // any index that references the effective_from column defensively.
+    await queryRunner.query(`
+      DO $$
+      DECLARE idx record;
+      BEGIN
+        FOR idx IN
+          SELECT indexname FROM pg_indexes
+          WHERE schemaname = 'freight'
+            AND tablename IN ('rates', 'weight_limit_rules')
+            AND indexdef ILIKE '%effective_from%'
+        LOOP
+          EXECUTE format('DROP INDEX IF EXISTS freight.%I', idx.indexname);
+        END LOOP;
+      END $$;
+    `);
+
+    await queryRunner.query(`ALTER TABLE freight.rates DROP COLUMN IF EXISTS effective_from;`);
+    await queryRunner.query(`ALTER TABLE freight.rates DROP COLUMN IF EXISTS effective_to;`);
+    await queryRunner.query(`ALTER TABLE freight.weight_limit_rules DROP COLUMN IF EXISTS effective_from;`);
+    await queryRunner.query(`ALTER TABLE freight.weight_limit_rules DROP COLUMN IF EXISTS effective_to;`);
+
+    // ── 3. One-rate-per-pattern partial unique indexes ─────────────────────
+    await queryRunner.query(`
+      CREATE UNIQUE INDEX IF NOT EXISTS "UQ_rates_pattern"
+      ON freight.rates (
+        rate_type,
+        COALESCE(container_type_id, '00000000-0000-0000-0000-000000000000'::uuid),
+        COALESCE(cargo_type_id, '00000000-0000-0000-0000-000000000000'::uuid),
+        COALESCE(trade_direction, '')
+      )
+      WHERE deleted_at IS NULL AND status <> 'SUPERSEDED';
+    `);
+
+    await queryRunner.query(`
+      CREATE UNIQUE INDEX IF NOT EXISTS "UQ_weight_limit_rules_pattern"
+      ON freight.weight_limit_rules (container_type_id, trade_direction)
+      WHERE deleted_at IS NULL;
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`DROP INDEX IF EXISTS freight."UQ_rates_pattern";`);
+    await queryRunner.query(`DROP INDEX IF EXISTS freight."UQ_weight_limit_rules_pattern";`);
+
+    await queryRunner.query(`ALTER TABLE freight.rates ADD COLUMN IF NOT EXISTS effective_from date;`);
+    await queryRunner.query(`UPDATE freight.rates SET effective_from = COALESCE(effective_from, created_at::date);`);
+    await queryRunner.query(`ALTER TABLE freight.rates ALTER COLUMN effective_from SET NOT NULL;`);
+    await queryRunner.query(`ALTER TABLE freight.rates ADD COLUMN IF NOT EXISTS effective_to date;`);
+
+    await queryRunner.query(`ALTER TABLE freight.weight_limit_rules ADD COLUMN IF NOT EXISTS effective_from date;`);
+    await queryRunner.query(`ALTER TABLE freight.weight_limit_rules ADD COLUMN IF NOT EXISTS effective_to date;`);
+
+    await queryRunner.query(`CREATE INDEX IF NOT EXISTS "IDX_rates_effective_from" ON freight.rates (effective_from);`);
+    await queryRunner.query(
+      `CREATE INDEX IF NOT EXISTS "IDX_weight_limit_rules_effective_from" ON freight.weight_limit_rules (effective_from);`,
+    );
+  }
+}
diff --git a/apps/edr-freight-api/src/modules/rule-engine/dto/create-rate.dto.ts b/apps/edr-freight-api/src/modules/rule-engine/dto/create-rate.dto.ts
index 995718135..9a4cd642b 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/dto/create-rate.dto.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/dto/create-rate.dto.ts
@@ -1,6 +1,6 @@
 import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 import { Transform } from 'class-transformer';
-import { IsDateString, IsIn, IsNumber, IsOptional, IsString, IsUUID, MaxLength, Min } from 'class-validator';
+import { IsIn, IsNumber, IsOptional, IsString, IsUUID, MaxLength, Min } from 'class-validator';
 import {
   RATE_APPLIES_TO,
   RATE_TRIGGERS,
@@ -51,15 +51,6 @@ export class CreateRateDto {
   @ApiProperty({ enum: RATE_UNITS, description: 'Unit basis for the rate' })
   @IsIn([...RATE_UNITS])
   rateUnit!: string;
-
-  @ApiProperty({ description: 'Date from which this rate is effective (ISO date)', example: '2025-01-01' })
-  @IsDateString()
-  effectiveFrom!: string;
-
-  @ApiPropertyOptional({ description: 'Date when this rate expires. Null = currently active', example: '2025-12-31' })
-  @IsOptional()
-  @IsDateString()
-  effectiveTo?: string;
 }
 
 export class SubmitRateForApprovalDto {
diff --git a/apps/edr-freight-api/src/modules/rule-engine/dto/create-weight-limit-rule.dto.ts b/apps/edr-freight-api/src/modules/rule-engine/dto/create-weight-limit-rule.dto.ts
index 6be37214b..eea223ae3 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/dto/create-weight-limit-rule.dto.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/dto/create-weight-limit-rule.dto.ts
@@ -1,6 +1,6 @@
-import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
+import { ApiProperty } from '@nestjs/swagger';
 import { Transform } from 'class-transformer';
-import { IsDateString, IsIn, IsNumber, IsOptional, IsUUID, Min } from 'class-validator';
+import { IsIn, IsNumber, IsUUID, Min } from 'class-validator';
 
 const TRADE_DIRECTIONS = ['IMPORT', 'EXPORT', 'BOTH', 'DOMESTIC'] as const;
 
@@ -21,13 +21,4 @@ export class CreateWeightLimitRuleDto {
   @Min(0)
   @Transform(({ value }) => Number(value))
   maxVgmTons!: number;
-
-  @ApiProperty({ description: 'Date from which this rule is active (ISO date)', example: '2024-01-01' })
-  @IsDateString()
-  effectiveFrom!: string;
-
-  @ApiPropertyOptional({ description: 'Date when this rule expires (ISO date). Null = currently active', example: '2025-12-31' })
-  @IsOptional()
-  @IsDateString()
-  effectiveTo?: string;
 }
diff --git a/apps/edr-freight-api/src/modules/rule-engine/entities/rate-unit.util.ts b/apps/edr-freight-api/src/modules/rule-engine/entities/rate-unit.util.ts
new file mode 100644
index 000000000..cef613412
--- /dev/null
+++ b/apps/edr-freight-api/src/modules/rule-engine/entities/rate-unit.util.ts
@@ -0,0 +1,71 @@
+import type { RateAppliesTo, RateTrigger, RateUnit } from './rate.entity';
+
+/**
+ * Which rate units make sense for a given rate shape. The weighting basis is
+ * driven by the *type* of thing being billed — a container leg bills per
+ * container, bulk freight per ton, an intercity move can be per-km, a
+ * cancellation is a flat/per-invoice fee, and overweight is always per excess
+ * ton. This keeps the rate table dynamic yet non-conflicting: the admin can
+ * only pick a unit the pricing engine knows how to apply.
+ *
+ * Returned lists are ordered with the most natural/default unit first.
+ */
+export function allowedRateUnits(input: {
+  appliesTo: RateAppliesTo;
+  trigger: RateTrigger;
+}): RateUnit[] {
+  const { appliesTo, trigger } = input;
+
+  // Surcharges (Applies to = Other) are governed by their trigger.
+  if (appliesTo === 'OTHER') {
+    switch (trigger) {
+      case 'OVERWEIGHT':
+        // Overweight always bills the excess tonnage — per ton, nothing else.
+        return ['PER_TON'];
+      case 'REEFER':
+      case 'HAZARDOUS':
+        // Scale with the freight shape: per container for boxes, per ton for bulk.
+        return ['PER_CONTAINER', 'PER_TON'];
+      case 'DEMURRAGE':
+        return ['PER_CONTAINER', 'PER_TON'];
+      case 'CANCELLATION':
+        return ['FLAT', 'PER_INVOICE'];
+      case 'CONSOLIDATION':
+        return ['PER_CONTAINER', 'FLAT'];
+      case 'SHIPPING_LINE':
+      case 'PIL_EXTRA_FEE':
+        return ['PER_CONTAINER', 'FLAT'];
+      default:
+        return ['FLAT', 'PER_TON', 'PER_CONTAINER'];
+    }
+  }
+
+  // Base freight + first/last mile scale with the cargo type.
+  switch (appliesTo) {
+    case 'CONTAINER':
+      return ['PER_CONTAINER', 'PER_WAGON'];
+    case 'BULK':
+      return ['PER_TON', 'PER_WAGON'];
+    case 'INTERCITY':
+      return ['PER_CONTAINER', 'PER_TON', 'PER_WAGON', 'PER_KM'];
+    case 'FIRST_MILE':
+    case 'LAST_MILE':
+      return ['PER_CONTAINER', 'PER_TON', 'PER_KM', 'FLAT'];
+    default:
+      return ['FLAT'];
+  }
+}
+
+/** The default (first / most natural) unit for a rate shape. */
+export function defaultRateUnit(input: { appliesTo: RateAppliesTo; trigger: RateTrigger }): RateUnit {
+  return allowedRateUnits(input)[0];
+}
+
+/** True when `unit` is a valid weighting basis for the given rate shape. */
+export function isRateUnitAllowed(input: {
+  appliesTo: RateAppliesTo;
+  trigger: RateTrigger;
+  unit: RateUnit;
+}): boolean {
+  return allowedRateUnits(input).includes(input.unit);
+}
diff --git a/apps/edr-freight-api/src/modules/rule-engine/entities/rate.entity.ts b/apps/edr-freight-api/src/modules/rule-engine/entities/rate.entity.ts
index b57b48cd8..50f8b3b99 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/entities/rate.entity.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/entities/rate.entity.ts
@@ -81,7 +81,6 @@ export type RateTrigger = typeof RATE_TRIGGERS[number];
 @Entity({ schema: 'freight', name: 'rates' })
 @Index(['rateType'])
 @Index(['status'])
-@Index(['effectiveFrom'])
 @Index(['containerTypeId'])
 @Index(['trigger'])
 export class Rate extends BaseEntity {
@@ -131,10 +130,4 @@ export class Rate extends BaseEntity {
 
   @Column({ name: 'approved_at', type: 'timestamptz', nullable: true })
   approvedAt?: Date | null;
-
-  @Column({ name: 'effective_from', type: 'date' })
-  effectiveFrom!: Date;
-
-  @Column({ name: 'effective_to', type: 'date', nullable: true })
-  effectiveTo?: Date | null;
 }
diff --git a/apps/edr-freight-api/src/modules/rule-engine/entities/weight-limit-rule.entity.ts b/apps/edr-freight-api/src/modules/rule-engine/entities/weight-limit-rule.entity.ts
index 39557eec9..b6b87b285 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/entities/weight-limit-rule.entity.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/entities/weight-limit-rule.entity.ts
@@ -5,7 +5,6 @@ import { ContainerType } from './container-type.entity';
 @Entity({ schema: 'freight', name: 'weight_limit_rules' })
 @Index(['containerTypeId'])
 @Index(['tradeDirection'])
-@Index(['effectiveFrom'])
 export class WeightLimitRule extends BaseEntity {
   @Column({ name: 'container_type_id', type: 'uuid' })
   containerTypeId!: string;
@@ -19,10 +18,4 @@ export class WeightLimitRule extends BaseEntity {
 
   @Column({ name: 'max_vgm_tons', type: 'numeric', precision: 8, scale: 3, nullable: true })
   maxVgmTons!: number;
-
-  @Column({ name: 'effective_from', type: 'date', nullable: true })
-  effectiveFrom!: Date;
-
-  @Column({ name: 'effective_to', type: 'date', nullable: true })
-  effectiveTo?: Date | null;
 }
diff --git a/apps/edr-freight-api/src/modules/rule-engine/interfaces/rates.repository.interface.ts b/apps/edr-freight-api/src/modules/rule-engine/interfaces/rates.repository.interface.ts
index 52b991155..24b3c3626 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/interfaces/rates.repository.interface.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/interfaces/rates.repository.interface.ts
@@ -4,6 +4,12 @@ import { Rate } from '../entities/rate.entity';
 export interface IRatesRepository {
   findById(id: string): Promise<Rate | null>;
   findLiveRates(): Promise<Rate[]>;
+  findByPattern(pattern: {
+    rateType: string;
+    containerTypeId?: string | null;
+    cargoTypeId?: string | null;
+    tradeDirection?: string | null;
+  }): Promise<Rate | null>;
   findAll(options?: FindManyOptions<Rate>): Promise<Rate[]>;
   findAndCount(options?: FindManyOptions<Rate>): Promise<[Rate[], number]>;
   create(data: Partial<Rate>): Promise<Rate>;
diff --git a/apps/edr-freight-api/src/modules/rule-engine/interfaces/weight-limit-rules.repository.interface.ts b/apps/edr-freight-api/src/modules/rule-engine/interfaces/weight-limit-rules.repository.interface.ts
index cedbd1eee..3c175df4e 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/interfaces/weight-limit-rules.repository.interface.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/interfaces/weight-limit-rules.repository.interface.ts
@@ -7,6 +7,11 @@ export interface IWeightLimitRulesRepository {
     containerTypeId: string,
     tradeDirection: string,
   ): Promise<WeightLimitRule[]>;
+  findByPattern(
+    containerTypeId: string,
+    tradeDirection: string,
+    excludeId?: string,
+  ): Promise<WeightLimitRule | null>;
   findAll(options?: FindManyOptions<WeightLimitRule>): Promise<WeightLimitRule[]>;
   findAndCount(options?: FindManyOptions<WeightLimitRule>): Promise<[WeightLimitRule[], number]>;
   create(data: Partial<WeightLimitRule>): Promise<WeightLimitRule>;
diff --git a/apps/edr-freight-api/src/modules/rule-engine/repositories/rates.repository.ts b/apps/edr-freight-api/src/modules/rule-engine/repositories/rates.repository.ts
index 0d49a0bf3..bbb5f2386 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/repositories/rates.repository.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/repositories/rates.repository.ts
@@ -16,15 +16,48 @@ export class RatesRepository implements IRatesRepository {
   }
 
   findLiveRates(): Promise<Rate[]> {
-    const now = new Date();
     return this.repo
       .createQueryBuilder('rate')
       .where('rate.status = :status', { status: 'LIVE' })
-      .andWhere('rate.effective_from <= :now', { now })
-      .andWhere('(rate.effective_to IS NULL OR rate.effective_to > :now)', { now })
       .getMany();
   }
 
+  /**
+   * Find a non-superseded rate matching an identity pattern — the same tuple the
+   * `UQ_rates_pattern` unique index enforces. Used to reject duplicates before
+   * insert so the admin gets a friendly error instead of a raw constraint fault.
+   * NULL scope columns are matched with IS NULL, mirroring the COALESCE index.
+   */
+  findByPattern(pattern: {
+    rateType: string;
+    containerTypeId?: string | null;
+    cargoTypeId?: string | null;
+    tradeDirection?: string | null;
+  }): Promise<Rate | null> {
+    const qb = this.repo
+      .createQueryBuilder('rate')
+      .where('rate.rate_type = :rateType', { rateType: pattern.rateType })
+      .andWhere('rate.status <> :superseded', { superseded: 'SUPERSEDED' });
+
+    if (pattern.containerTypeId) {
+      qb.andWhere('rate.container_type_id = :containerTypeId', { containerTypeId: pattern.containerTypeId });
+    } else {
+      qb.andWhere('rate.container_type_id IS NULL');
+    }
+    if (pattern.cargoTypeId) {
+      qb.andWhere('rate.cargo_type_id = :cargoTypeId', { cargoTypeId: pattern.cargoTypeId });
+    } else {
+      qb.andWhere('rate.cargo_type_id IS NULL');
+    }
+    if (pattern.tradeDirection) {
+      qb.andWhere('rate.trade_direction = :tradeDirection', { tradeDirection: pattern.tradeDirection });
+    } else {
+      qb.andWhere('rate.trade_direction IS NULL');
+    }
+
+    return qb.getOne();
+  }
+
   findAll(options?: FindManyOptions<Rate>): Promise<Rate[]> {
     return this.repo.find(options);
   }
diff --git a/apps/edr-freight-api/src/modules/rule-engine/repositories/weight-limit-rules.repository.ts b/apps/edr-freight-api/src/modules/rule-engine/repositories/weight-limit-rules.repository.ts
index 0d151c561..87d2febba 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/repositories/weight-limit-rules.repository.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/repositories/weight-limit-rules.repository.ts
@@ -22,7 +22,6 @@ export class WeightLimitRulesRepository implements IWeightLimitRulesRepository {
     containerTypeId: string,
     tradeDirection: string,
   ): Promise<WeightLimitRule[]> {
-    const now = new Date();
     return this.repo
       .createQueryBuilder('rule')
       .innerJoinAndSelect('rule.containerType', 'ct')
@@ -31,11 +30,27 @@ export class WeightLimitRulesRepository implements IWeightLimitRulesRepository {
         dir: tradeDirection,
         both: 'BOTH',
       })
-      .andWhere('rule.effective_from <= :now', { now })
-      .andWhere('(rule.effective_to IS NULL OR rule.effective_to > :now)', { now })
       .getMany();
   }
 
+  /**
+   * Find a rule matching the (containerType, tradeDirection) identity — the
+   * tuple enforced by `UQ_weight_limit_rules_pattern`. Used to reject duplicates
+   * before insert. Optionally excludes a row by id so updates don't self-collide.
+   */
+  findByPattern(
+    containerTypeId: string,
+    tradeDirection: string,
+    excludeId?: string,
+  ): Promise<WeightLimitRule | null> {
+    const qb = this.repo
+      .createQueryBuilder('rule')
+      .where('rule.container_type_id = :containerTypeId', { containerTypeId })
+      .andWhere('rule.trade_direction = :tradeDirection', { tradeDirection });
+    if (excludeId) qb.andWhere('rule.id <> :excludeId', { excludeId });
+    return qb.getOne();
+  }
+
   findAll(options?: FindManyOptions<WeightLimitRule>): Promise<WeightLimitRule[]> {
     return this.repo.find(options);
   }
diff --git a/apps/edr-freight-api/src/modules/rule-engine/services/rates.service.ts b/apps/edr-freight-api/src/modules/rule-engine/services/rates.service.ts
index c3ab6bab0..2a717366d 100644
--- a/apps/edr-freight-api/src/modules/rule-engine/services/rates.service.ts
+++ b/apps/edr-freight-api/src/modules/rule-engine/services/rates.service.ts
@@ -1,8 +1,15 @@
-import { BadRequestException, Inject, Injectable, NotFoundException } from '@nestjs/common';
+import {
+  BadRequestException,
+  ConflictException,
+  Inject,
+  Injectable,
+  NotFoundException,
+} from '@nestjs/common';
 import { CreateRateDto } from '../dto/create-rate.dto';
 import { UpdateRateDto } from '../dto/update-rate.dto';
 import { Rate } from '../entities/rate.entity';
 import { deriveRateType } from '../entities/rate-type.util';
+import { allowedRateUnits, isRateUnitAllowed } from '../entities/rate-unit.util';
 import { IRatesRepository, RATES_REPOSITORY } from '../interfaces/rates.repository.interface';
 
 @Injectable()
@@ -27,7 +34,7 @@ export class RatesService {
 
     const [data, total] = await this.repository.findAndCount({
       where,
-      order: { effectiveFrom: 'DESC' },
+      order: { createdAt: 'DESC' },
       skip: (page - 1) * pageSize,
       take: pageSize,
     });
@@ -46,6 +53,49 @@ export class RatesService {
     return entity;
   }
 
+  /**
+   * Normalise + validate the weighting unit for a rate shape. Overweight is
+   * always billed per excess ton, so its unit is forced to PER_TON regardless
+   * of what the client sent. Every other shape must pick a unit the pricing
+   * engine can actually apply (see `allowedRateUnits`).
+   */
+  private resolveRateUnit(
+    appliesTo: Rate['appliesTo'],
+    trigger: Rate['trigger'],
+    requestedUnit: Rate['rateUnit'],
+  ): Rate['rateUnit'] {
+    // Overweight is per-ton, full stop.
+    if (trigger === 'OVERWEIGHT') return 'PER_TON';
+
+    if (!isRateUnitAllowed({ appliesTo, trigger, unit: requestedUnit })) {
+      const allowed = allowedRateUnits({ appliesTo, trigger }).join(', ');
+      throw new BadRequestException(
+        `Rate unit "${requestedUnit}" is not valid for this rate. Allowed: ${allowed}.`,
+      );
+    }
+    return requestedUnit;
+  }
+
+  /**
+   * Reject a second rate with the same identity pattern (rateType + scope). With
+   * effective-date windows gone, two LIVE/DRAFT rates for the same pattern would
+   * make pricing ambiguous — so we allow exactly one per pattern.
+   */
+  private async assertNoDuplicatePattern(pattern: {
+    rateType: string;
+    containerTypeId: string | null;
+    cargoTypeId: string | null;
+    tradeDirection: string | null;
+    ignoreId?: string;
+  }): Promise<void> {
+    const existing = await this.repository.findByPattern(pattern);
+    if (existing && existing.id !== pattern.ignoreId) {
+      throw new ConflictException(
+        'A rate for this exact combination already exists. Edit or delete the existing rate instead of creating a duplicate.',
+      );
+    }
+  }
+
   /** Create a rate in DRAFT status. */
   async create(dto: CreateRateDto, proposedByStaffId: string): Promise<Rate> {
     const appliesTo = dto.appliesTo as Rate['appliesTo'];
@@ -57,25 +107,28 @@ export class RatesService {
     const cargoTypeId = isSurcharge ? null : (dto.cargoTypeId ?? null);
     const tradeDirection = isSurcharge ? null : (dto.tradeDirection ?? null);
 
+    const rateType = deriveRateType({
+      appliesTo,
+      trigger,
+      tradeDirection,
+      isBulk: Boolean(cargoTypeId),
+    });
+    const rateUnit = this.resolveRateUnit(appliesTo, trigger, dto.rateUnit as Rate['rateUnit']);
+
+    await this.assertNoDuplicatePattern({ rateType, containerTypeId, cargoTypeId, tradeDirection });
+
     return this.repository.create({
       appliesTo,
       trigger,
-      rateType: deriveRateType({
-        appliesTo,
-        trigger,
-        tradeDirection,
-        isBulk: Boolean(cargoTypeId),
-      }),
+      rateType,
       containerTypeId,
       cargoTypeId,
       tradeDirection,
       currency: dto.currency ?? 'USD',
       rateValue: dto.rateValue,
-      rateUnit: dto.rateUnit as Rate['rateUnit'],
+      rateUnit,
       status: 'DRAFT',
       proposedByStaffId,
-      effectiveFrom: new Date(dto.effectiveFrom),
-      effectiveTo: dto.effectiveTo ? new Date(dto.effectiveTo) : undefined,
     });
   }
 
@@ -110,22 +163,34 @@ export class RatesService {
         ? dto.tradeDirection
         : existing.tradeDirection;
 
-    updates.containerTypeId = containerTypeId;
-    updates.cargoTypeId = cargoTypeId;
-    updates.tradeDirection = tradeDirection;
+    updates.containerTypeId = containerTypeId ?? null;
+    updates.cargoTypeId = cargoTypeId ?? null;
+    updates.tradeDirection = tradeDirection ?? null;
     // Keep the derived rateType in sync with whatever changed.
-    updates.rateType = deriveRateType({
+    const rateType = deriveRateType({
       appliesTo,
       trigger,
       tradeDirection,
       isBulk: Boolean(cargoTypeId),
     });
+    updates.rateType = rateType;
+
+    // Re-validate the unit against the (possibly changed) shape; overweight is
+    // forced to PER_TON.
+    const requestedUnit = (dto.rateUnit as Rate['rateUnit']) ?? existing.rateUnit;
+    updates.rateUnit = this.resolveRateUnit(appliesTo, trigger, requestedUnit);
+
+    // Guard the pattern uniqueness for the new identity, ignoring this row.
+    await this.assertNoDuplicatePattern({
+      rateType,
+      containerTypeId: updates.containerTypeId,
+      cargoTypeId: updates.cargoTypeId,
+      tradeDirection: updates.tradeDirection,
+      ignoreId: id,
+    });
 
     updates.currency = dto.currency ?? existing.currency ?? 'USD';
     if (dto.rateValue !== undefined) updates.rateValue = dto.rateValue;
-    if (dto.rateUnit) updates.rateUnit = dto.rateUnit as Rate['rateUnit'];
-    if (dto.effectiveFrom) updates.effectiveFrom = new Date(dto.effectiveFrom);
-    if (dto.effectiveTo) updates.effectiveTo = new Date(dto.effectiveTo);
     const updated = await this.repository.update(id, updates);
     if (!updated) throw new NotFoundException(`Rate ${id} not found`);
     return updated;