Guidance

Minimum certification requirements for businesses to use a mass balance approach for Plastic Packaging Tax

Published 28 August 2026

1. Getting certified by a scheme that meets the minimum requirements

You will need to choose a scheme that meets the minimum requirements.

HMRC does not regulate certification schemes. It is your responsibility to make sure the scheme you have chosen is meeting the minimum requirements.

To meet the minimum requirements, the certification scheme you choose will require you to:

• operate a site-level mass balance system with a 3-month mass balance approach accounting period and no negative balance at any time
• use fuel-excluded attribution where your process produces outputs that include fuel-use products
• calculate and apply site-specific conversion factors where you calculate attributed recycled plastic
• keep records for 6 years

If you are not sure whether a certification scheme meets the minimum requirements, you should contact them to find out about their certification process and audit requirements.

Read the other documents in this guidance to find out more about what certification scheme operators have to do.

The certification scheme will decide which certification body will check your business.

1.1 How the certification body will check your business

You will be certified by a certification body, who will check your business is meeting the minimum requirements set by your chosen certification scheme.

Certification bodies must be accredited by signatories to the Global Accreditation Cooperation Incorporated Multilateral Recognition Arrangement. In the UK, this is the United Kingdom Accreditation Service.

Read the other documents in this guidance to find out more about what certification bodies have to do.

2. How to operate your mass balance approach accounting period

Your accounting period (also known as the balancing period) is the time period for making sure the amount of chemically recycled material received at your site balances with the amount that you attribute to your outputs.

You must operate a 3-month accounting period with no negative balance at any point in the period.

If you’re liable for Plastic Packaging Tax, your accounting period dates do not need to be the same as your Plastic Packaging Tax accounting period.

Your accounting period dates must:

• follow on from each other
• have no gaps between them
• start on the day you were certified

3. Calculating attributed recycled plastic

The minimum requirements for calculating attributed recycled plastic are that you must:

• apply conversion factors
• apply the fuel-excluded attribution method
• consider dual-use output products
• transfer credits if you choose to

3.1 How to apply conversion factors

You must apply a conversion factor to:

• account for losses during the processing of the chemically recycled material
• work out how much of it is available for attribution to the output products

The conversion factor must be:

• based on the operational data of the processing unit
• specific to the site
• applied at any stage where the amount of chemically recycled input material is changed

3.2 When to apply the fuel-excluded attribution method

At certain stages of the supply chain, you may need to co-process chemically recycled material with other material, such as non-recycled (virgin) material, through complex refinery and petrochemical processes that produce multiple output products. These outputs can be used for different purposes, including as fuels or in the production of fuels.

To meet the minimum requirements, you must attribute chemically recycled material using the fuel-excluded attribution method when you produce multiple output products that include fuel use products.

3.3 When to use dual-use factors

When products have dual-use, you must use dual-use factors in the mass balance calculation.

If you co-process chemically recycled material with virgin material through refinery or petrochemical processes, you must:

• categorise your output products
• apply a dual-use factor to each product

3.4 What to do if you can transfer credits

Recovered material credits are the amount of attributed chemically recycled material that you have in your site-level mass balance during an accounting period.

Example

Company A has 100 tonnes of attributed chemically recycled material in its site-level mass balance, so it has 100 tonnes of recovered material credits.

Some businesses are connected by a physical pipeline. While you must keep a site level mass balance, you can transfer recovered material credits between your sites if you meet certain conditions, such as both sites being connected by a physical pipeline.

4. Records you must keep

To be certified, you must keep:

• a valid certificate
• attribution declarations for each batch of material
• site-specific mass balance records

You must keep these records in writing (including in electronic form) for 6 years.

4.1 What a valid certificate must include

Your certificate must include the:

• business addresses where the certification applies
• dates it is valid from
• details of the certified materials covered by the certificate

You will become certified after you have passed your audit by a certification body.

4.2 When you must complete an attribution declaration

An attribution declaration must be completed for each single delivery or quantity (batch) of material that has chemically recycled material inputs attributed using a mass balance approach.

The attribution declaration is for you and your suppliers to show that the chemically recycled material has been handled and attributed to the certification requirements set by your scheme.

You need a new attribution declaration every time the material is passed between businesses in the supply chain.

A complete attribution declaration must have:

• the total amount of recycled material covered by the declaration
• a unique batch number
• the date of dispatch
• the name and address of the supplier and recipient

4.3 How to record site-specific mass balance records

After you’ve received an attribution declaration, you must record and verify the information on it using site-specific mass balance records.

The site-specific mass balance records must include:

• virgin and recycled inputs and outputs
• accounting period
• opening and closing stock
• conversion factors