Custom Discount

A Custom Discount holds product, order and shipping offers in one discount, and lets each offer read its value from a metafield you already own. Instead of typing a price for every product, you keep the numbers on your variants — where your ERP, your spreadsheet or your supplier feed already puts them — and the discount looks them up as the cart is priced.

Use it when the numbers belong to the products rather than to the promotion: wholesale price lists, per-item contract pricing, case prices that differ by SKU. If the same value applies to everything in the promotion, Multi-offer is simpler.

You probably do not need a metafield

Most of this page is about reading prices from your own product data, which is the advanced half of this discount type. A plain percentage off, an amount off, a fixed price, or free shipping needs none of it — leave Read prices from a product metafield switched off and skip to Selecting items with cart groups.

You only need a metafield when the price is different for every product and already lives in your own data.

Three pages cover this discount type. This one is the reference. Set up the price metafield walks through creating the metafield in Shopify from nothing. Custom Discount examples has thirteen complete setups to copy.

Setup

1. Open Discounts, click Create discount, and choose Custom Discount.

2. Choose the discount method and name the discount.

   Automatic applies on its own. Discount code asks the customer to enter a code. The title is what the customer sees; tick Add internal title for reference if you want a private name as well.

3. Choose where the discount applies.

   All markets, or only the markets you pick. Each offer below can narrow this further.

4. Turn on Read prices from a product metafield, if your prices live in your own data.

   Enter the namespace and key of the metafield that holds them. This address applies to the whole discount — one metafield per discount, read from every variant in the cart.

   

5. Add cart groups to describe which items you mean.

   A cart group is a named selection of items — “Case packs”, “Spring range” — built from conditions. Groups are defined once and reused by any offer. All items is built in.

6. Turn on the offers you need, and point each one at a group.

   Product, order and shipping offers each have their own value, their own items and their own requirements.

7. Set requirements, overlap handling, combinations, markets and dates, then save.

Reading prices from a product metafield

ノート

This section is the reference for how the value is read. For a step-by-step walkthrough of creating the metafield in Shopify, filling it in and pointing the discount at it, see Set up the price metafield.

Where the value lives

The discount reads a variant metafield. Shopify shows product metafields and variant metafields on the same page, and only the variant one is read.

The most common setup mistake

Filling in Product metafields → Volume pricing does nothing. The value must be under Variant metafields.

What the value looks like

The metafield is a JSON object of flat name-and-value pairs. You choose the names.

{ "v": 1, "qty6": 850, "qty12": 750, "floor": 700, "pack": 12, "season": "ss26" }

• "v": 1 is required. It is the format version, and it lets the shape grow later without changing what today’s values mean. A metafield without it, or with any other value, is ignored.
• Numbers are amounts, or values a condition can compare. 850 and 12 above.
• Text is for selecting items, never for money. "ss26" above.
• Anything else — true, a nested object, a list — is ignored.
• Two names are reserved: v and unit. Every other name is yours.

Field names use letters, digits, _ and -, and start with a letter or _.

Whole minor units, or plain prices

By default a number is a whole minor unit of your store currency, so 850 means 8.50 and 249 means 2.49. This is the format most ERP exports already use, and it cannot be misread.

If you would rather write prices the way you say them, add "unit": "major":

{ "v": 1, "unit": "major", "qty6": 8.50, "qty12": 7.50, "floor": 7 }

Both files above mean the same thing. Some rules to know:

• The setting applies to the whole metafield, not to one field. Pick one style per variant.
• Under "major", an amount with more decimals than your currency has is ignored — 1.999 in a two-decimal currency, 15.5 in yen. The app will not round it into money.
• "unit" must be exactly minor or major. Any other word and the whole metafield is ignored, so a typo cannot quietly change what your prices mean.
• A percentage is never affected by this setting. It is always read as written, so 10 is 10% in both styles, and 12.5 is 12.5%.

Pointing an offer at a field

Set a product offer’s Discount value to Price from product data.

Setting	What it does
Field	The name in the metafield that holds this offer’s number.
What the number means	Fixed price for the item — the item is sold at that price. Amount off each item — that much comes off each unit. Percentage off — that percentage comes off.
Tiered by line quantity	Reads qty6, qty12 and so on, using the highest tier the line’s quantity reaches.
Floor field	Names a field holding the lowest price the item may reach.
Cap field	Names a field holding the most that may come off one unit.

Three things that are easy to miss:

• Tiers are per line. Six of a variant in one line reaches tier 6. Three plus three in two separate lines does not.
• A field name used for tiers must not end in a digit, because the tier number is added to the end of it. price_1 with tiers on would read price_12 as tier 2. The app refuses that combination when you save.
• A floor or cap you name must be readable on the variant. If you point an offer at a cap field and a variant has no usable cap, that item gets no discount — the limit is never dropped silently.

An item gets no discount, rather than a wrong one, whenever the number is missing, zero, negative, text, or not a usable amount. That is deliberate: a discount that cannot be computed exactly does not run.

Validating the metafield in Shopify

Give the metafield a definition with a JSON schema and Shopify refuses a broken value at the moment someone saves it — in the admin, in the bulk editor and through the API. Create the definition under Settings → Metafields and metaobjects → Variants, choose the JSON type, and paste this as the schema:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "required": ["v"],
  "minProperties": 2,
  "maxProperties": 40,
  "properties": {
    "v": { "type": "integer", "enum": [1] },
    "unit": { "type": "string", "enum": ["minor", "major"] },
    "label": { "type": "string", "maxLength": 40 }
  },
  "patternProperties": {
    "^(qty|price|wholesale|floor|cap|min|max)[0-9]*$": {
      "type": "number", "minimum": 0, "maximum": 100000000
    }
  },
  "additionalProperties": { "type": ["number", "string", "boolean"] }
}

That schema refuses a wrong version, a list instead of an object, a nested object, a negative amount, and a misspelled unit. Shopify does not enforce field-name patterns on a metafield schema, so field names are checked by the app instead, when you type one into an offer or a condition.

Selecting items with cart groups

A cart group is a named selection of cart items. Offers refer to groups by name, so one group can target one offer and gate another.

Each group matches all, any or none of its conditions. “None” is the complement: the group holds every item that matches none of the conditions.

Conditions available on a Custom Discount:

Group	Conditions
Item	Specific products, specific variants, specific collections, line quantity, line subtotal, line attribute, compare-at price, has selling plan
Price data	Price data field, Price data number — shown only while Read prices from a product metafield is on, and only on product offers
Cart	Cart subtotal, cart quantity, cart attribute, retail location
Customer	Customer tags, customer logged in, customer is B2B, company
Shipping	Shipping type, shipping method, country, province or state, city, postal code — shipping offers only

Product tags and customer order count are not available on this discount type.

Price data conditions

Price data field selects items by a piece of text in the metafield — a season code, a supplier, a contract tier. Price data number selects them by a number in it.

A number condition offers equals, is greater than or equal to, is less than or equal to, and is between. It reads the number exactly as written, so it is unaffected by the unit setting — pack of 12 is twelve whether your amounts are in minor or major units.

What happens when an item has no price data, or not that field:

• A positive condition does not match it.
• A negative text condition — is not one of, does not contain — does match it. The field genuinely is not there.
• A number condition never matches it, whichever comparison you chose. “Less than or equal to 6” does not match an item with no number to compare.
• A group set to none therefore includes items with no price data, which is usually what you want from “everything except the case packs”.

Requirements

Requirements gate an offer on a whole group rather than on each item. Choose a group, a measure and a comparison.

Measure	What it counts
Subtotal, compare-at subtotal	Money in the group
Quantity	Units in the group
Lines, products, variants	How many of each are in the group
Groups matched	How many of several named groups the cart has items from

Comparisons are equals, is greater than or equal to, is less than or equal to and is divisible by. Divisible by works on the whole number measures — quantity, lines, products, variants, groups matched — and is how you express “every third item” or “sold in pairs”.

Overlaps, limits and combinations

• When offers overlap, choose to apply the first matching offer, the one that saves the most, or all of them. Applying all is unavailable while an offer reads prices from product data.
• An overall item limit caps how many units the whole discount may touch, taking the highest-value, lowest-value or first items in the cart.
• Combinations decide whether this discount runs alongside product, order and shipping discounts. See Combinations.
• Discount tags let you label a discount for your own reporting, up to 20 tags. Stacking tags, which let two product discounts apply to the same item, require Shopify Plus.
• Usage limits and scheduling work as they do everywhere else. See Usage limits and scheduling.

Markets and currency

Amounts in the metafield are in your store currency. With Convert to customer’s currency on, they are converted at Shopify’s rate for the customer’s currency. With it off, an offer that reads prices from product data applies only to customers paying in your store currency — it will not treat your number as though it were the customer’s currency. Percentages are unaffected either way. See Markets and currency.

Who can use the discount

Limit the discount to signed-in customers, to customer tags, to B2B companies, or to a Shopify customer segment. See Customer eligibility.

Test mode

Test mode makes a saved discount apply only to a signed-in customer whose customer record carries the tag dos-test. Everyone else shops as if the discount did not exist. It is the safe way to try pricing on a live store before anyone else sees it: turn it on, add the tag to your own customer account, check the cart, then turn it off.

Check a product

Check a product answers “what would this discount do to this item?” without touching a cart. Pick a product and a variant, and the app reads that variant’s real metafield and runs the same arithmetic the discount uses.

For an offer that reads prices, you get a row per quantity — quantity 1 and every tier present — with the discount per item, the resulting price, and a plain reason when nothing applies.

For an offer whose group uses Price data conditions, you get the conditions instead, each with what the engine decides for that variant, and a verdict.

Use it whenever a discount is not behaving: it tells you whether the data or the discount is at fault, and names the field when the data is.

Keeping the metafield up to date

You rarely want to edit these by hand. In rough order of how many variants you have:

A few variants — the product page. Open the product, find Variant metafields, edit the value. Good for a correction, painful past a handful.

Tens to hundreds — Shopify’s bulk editor. The bulk editor can show the variant metafield as a column, so you can fill or paste a whole column in one pass. Reach it from a product’s variant list or from the products list, and use Columns to add the field. Shopify’s bulk editing guide has the current navigation.

Make sure you are editing variants, not products. The product-level column of the same name is a different field, and nothing reads it.

Hundreds to thousands — a spreadsheet. Build the JSON in a spreadsheet so every row has an identical shape, then paste the column into the bulk editor. A formula like ="{""v"":1,""qty6"":"&B2&",""qty12"":"&C2&"}" keeps the punctuation right. If your export tool supports metafield columns in a CSV, the same column works there — check Shopify’s import and export guide for what your plan supports.

On a schedule, or from another system — the API. The metafieldsSet mutation writes metafields in batches and is the right tool for a nightly sync from an ERP. If your source already emits JSON, write it straight through — the app reads 79, 79.0 and 7.9e1 as the same amount, so you do not need to reformat your exporter’s numbers.

Without code — Shopify Flow. A workflow can write a metafield when something changes, which covers rules like “copy the supplier price into the wholesale field” without a developer.

Publish the definition first

Whichever route you choose, create the metafield definition with the schema above before you load data. Shopify then rejects a malformed row as it is written, instead of letting it sit quietly in your catalogue not discounting.

Examples

Thirteen complete setups live on their own page, from a plain 20% off a collection to per-account contract pricing read from your data: Custom Discount examples.

A few of them:

Example	Needs a metafield?
A plain percentage off a collection	No
A product discount and free shipping in one discount	No
Wholesale case pricing, a different price per SKU at 6 and at 12	Yes
A protected floor so a deep tier never sells below cost	Yes
Contract pricing for tagged customers only	Yes
Case packs only, chosen by a number in your data	Yes
Clearing a season by a text field	Yes

Limits and what to expect

• Configuration size. A discount’s configuration is capped at 10 kB, shown live as you edit. Long lists of specific products are what fill it; collections and conditions are compact.
• Very large carts. Shopify gives a discount a fixed amount of work per cart. On our test store a discount with a Price data condition applied to carts of up to 172 different products and stopped applying beyond that; without such a condition the same discount reached 180. When the limit is passed the discount applies nothing — it never applies partially or wrongly.
• Quantities are not a constraint in the same way. A single line of 3,000 units prices correctly.
• Price data is for product offers only. Price data conditions and the Price from product data value are available on product offers; order and shipping offers do not read the metafield, and the app refuses that combination when you save.

If something is not applying

Work through these in order.

1. Check a product on a variant you expect to discount. It names the reason.
2. Confirm the value is under Variant metafields, not product metafields.
3. Confirm "v": 1 is present.
4. Confirm the units. 8.5 without "unit": "major" is eight and a half minor units, not 8.50.
5. Confirm the field name in the offer matches the field name in the data, exactly.
6. For tiers, confirm the line’s quantity reaches a tier, and that the field name does not end in a digit.
7. If you named a floor or cap field, confirm every variant has a usable value in it.

Still stuck? See Discount not applying.