A4 Board Backed Envelopes

Features & Benefits

• A4 board-backed envelopes
• Nominal size of 229mm x 324mm
• Approximately 9 x 12.75 inches
• Measurements shown as width x height
• Suitable for holding standard A4 documents without folding
• Rigid board backing helps reduce bending and creasing
• Brown kraft paper front
• Printed DO NOT BEND message
• Red warning print stands out clearly during handling
• Peel-and-seal adhesive closure
• Quick and straightforward to close
• No separate packaging tape normally required
• Flat construction suits documents and other slim items
• Smooth exterior provides space for addresses and courier labels
• Suitable for postal and courier deliveries
• Useful for certificates, photographs, prints and business documents
• Lightweight alternative to rigid postal cartons for compatible flat items
• Helps protect document corners and edges
• Suitable for offices, retailers, photographers and e-commerce businesses
• Sold individually for flexible ordering
• Clean and unused paper components may be recyclable where local facilities accept them
• Free UK delivery

Common Uses

Our A4 Board-Backed Envelopes are suitable for posting and protecting:

• A4 documents
• Certificates
• Contracts
• Legal papers
• Business correspondence
• Reports
• Presentations
• Brochures
• Catalogues
• Photographs
• Art prints
• Illustrations
• Drawings
• Plans
• Manuscripts
• Greeting cards
• Invitations
• Event materials
• Educational documents
• Training materials
• Examination papers
• Application forms
• Product literature
• Promotional inserts
• Calendars
• Stickers and transfers
• Collectable cards
• Thin books and publications
• Flat product samples
• Other compatible slim items

Always check the complete width, height, thickness and rigidity of the contents before selecting an envelope.

A4 Board-Backed Envelopes

Our A4 Board-Backed Envelopes provide a practical postal solution for documents and other flat products that require more protection than a standard paper envelope can provide.

Each envelope combines a brown kraft paper front with a rigid board backing. The board helps support the contents during handling and reduces the risk of bending, folding and creasing.

The front displays the message PLEASE DO NOT BEND in clear red lettering. This warning helps postal and courier workers identify that the contents should remain flat.

A peel-and-seal adhesive strip provides a convenient closure. Simply insert the contents, remove the release strip, fold the flap over the opening and press firmly across the complete adhesive area.

Measuring approximately 229mm wide x 324mm high, the envelope is designed to accommodate standard A4 documents without requiring them to be folded.

We sell these A4 Board-Backed Envelopes individually, allowing customers to order the precise number required.

A4 Board-Backed Envelope Size and Specification

The product specification is:

• Nominal size: 229mm x 324mm
• Approximate imperial size: 9 x 12.75 inches
• Measurement order: width x height
• Paper size suitability: A4
• Standard A4 paper size: 210mm x 297mm
• Front material: brown kraft paper
• Backing: rigid board
• Colour: brown
• Closure: peel-and-seal adhesive flap
• Printed message: PLEASE DO NOT BEND
• Print colour: red
• Format: portrait
• Construction: flat, non-gusseted envelope
• Cushioning: none
• Sales unit: sold individually

The dimensions are nominal manufacturing measurements. Therefore, small production tolerances may apply.

The paper weight, board thickness and recycled-content percentage are not currently confirmed. Consequently, do not assume a particular gsm, board grade or environmental specification without supporting documentation.

Understanding the 229mm x 324mm Measurements of A4 board backed envelopes

We show the dimensions as width x height.

The first measurement, 229mm, represents the nominal width across the envelope.

The second measurement, 324mm, represents the nominal height from the bottom edge to the opening beneath the closure flap.

The sealing flap extends beyond the envelope opening and folds down after filling. It should not be treated as additional usable height.

A standard sheet of A4 paper measures 210mm x 297mm. Therefore, the nominal envelope dimensions provide additional room around an A4 sheet for insertion and removal.

However, seams, folds and manufacturing tolerances may reduce the precise usable internal space. Additionally, thick contents use more of the available width and height.

Do not select the envelope according to face dimensions alone when sending several documents, booklets or other items with noticeable thickness.

Suitable for A4 Documents Without Folding

The 229mm x 324mm format is designed for standard A4 documents measuring 210mm x 297mm.

This allows customers to post suitable papers without folding them into a smaller envelope. Keeping documents flat can improve their presentation and reduce unwanted fold lines.

The envelope may suit:

• Certificates that must remain presentable
• Contracts requiring signatures
• Formal correspondence
• Reports and presentations
• Photographs and art prints
• Brochures and promotional literature
• Educational and training materials
• Application documents
• Legal and financial papers
• Customer paperwork

Although the board backing helps support the contents, it does not make the envelope completely rigid or impossible to bend.

Important, valuable or irreplaceable documents may require additional rigid protection.

Rigid Board Backing

The board backing forms the reinforced rear panel of the envelope.

This panel helps support flat contents and reduces the likelihood of ordinary bending or creasing during handling. It also provides a firmer base when inserting papers, applying labels and preparing the envelope for dispatch.

The board may help protect:

• Document corners
• Paper edges
• Photographic prints
• Certificates
• Thin card products
• Flat artwork
• Promotional materials
• Other compatible slim items

However, the board can still bend, crease or become crushed when exposed to excessive pressure.

The envelope should not be treated as:

• Completely rigid
• Crushproof
• Waterproof
• Puncture-proof
• Suitable for highly fragile goods
• A replacement for a postal carton
• Guaranteed to remain flat in every delivery network

Where the contents have significant value or must remain perfectly flat, add suitable rigid inserts or use a stronger postal container.

Brown Kraft Paper Front

The brown kraft paper front provides a practical surface for addressing and labelling the envelope.

Customers can apply:

• Courier labels
• Postage labels
• Printed address labels
• Return-address labels
• Tracking barcodes
• Handling instructions
• Branded stickers
• Reference numbers
• Order information

The natural brown appearance suits business, office, retail and e-commerce applications.

Apply labels to a clean, dry and flat area. Press firmly around every edge and make sure important barcodes remain smooth and readable.

Avoid applying delivery labels across the closure flap or over heavily creased sections.

Pens, inks, stamps and label adhesives can perform differently on paper surfaces. Therefore, test your chosen method before preparing important or regular mailings.

Printed “DO NOT BEND” Message

The front of the envelope carries the instruction DO NOT BEND in red lettering.

The contrasting print helps draw attention to the fact that the contents should remain flat during sorting, storage and delivery.

This message is particularly useful when sending:

• Certificates
• Photographs
• Artwork
• Contracts
• Formal papers
• Collectable cards
• Presentation documents
• Printed promotional materials

However, the wording provides a handling instruction rather than a guarantee.

Postal and courier systems may still expose the envelope to pressure, impact, stacking and automated sorting equipment. Therefore, the sender must use enough protection for the value and sensitivity of the contents.

The exact position, colour tone, size and appearance of the printed wording may vary slightly between production batches.

Peel-and-Seal Adhesive Closure

Each A4 Board-Backed Envelope includes a peel-and-seal adhesive closure.

The adhesive is protected by a removable release strip until the envelope is ready to close.

To seal the envelope:

1. Place the contents completely inside.
2. Make sure the papers sit below the opening.
3. Check that nothing obstructs the flap.
4. Confirm the contents and delivery address.
5. Keep the sealing area clean and dry.
6. Remove the release strip.
7. Fold the flap evenly over the opening.
8. Press firmly across the complete adhesive area.
9. Inspect the closure before dispatch.

The peel-and-seal design normally removes the need to moisten the adhesive or apply separate packaging tape.

Once the adhesive has made firm contact, repositioning may not be possible. Therefore, check the contents before removing the release strip.

Dust, grease, paper fibres, moisture and low temperatures may reduce adhesive performance.

A4 board backed envelopes with Tamper-Evident Closure

The permanent adhesive flap provides visible evidence if someone opens the envelope after sealing.

Opening the flap may tear, crease or lift the paper surface. Consequently, the envelope cannot normally be opened and resealed without leaving some indication of interference.

However, the closure is tamper-evident rather than tamper-proof.

A determined person may still cut, tear or otherwise damage the envelope. Sensitive or valuable documents may require additional security measures, including:

• Tamper-evident internal packaging
• Security labels
• Tracked delivery
• Signed delivery
• Appropriate transit insurance
• A more secure outer container

Inspect the sealed flap and complete envelope before dispatch.

Flat, Non-Gusseted Construction

These envelopes have a flat, non-gusseted design.

They are best suited to documents, photographs, thin brochures and other slim contents.

Because the sides do not expand like a gusseted envelope, excessive thickness may:

• Stretch the paper
• Distort the board
• Place pressure on the seams
• Prevent the flap from closing correctly
• Reduce the usable width and height
• Increase the risk of damage
• Change the completed postal dimensions

Do not force thick books, bulky products or several large items into the envelope.

If the contents create a pronounced bulge, use a suitable expandable envelope, padded mailer or postal carton.

Choosing the Correct Envelope for Your Contents

Measure the complete item before inserting it into the envelope.

Consider:

• Width
• Height
• Thickness
• Rigidity
• Weight
• Value
• Surface finish
• Sensitivity to bending
• Presence of sharp corners
• Need for moisture protection

When sending several sheets or items together, arrange them in the intended position and measure the combined thickness.

Allow sufficient clearance around the contents so they can enter without scraping against the seams or becoming trapped beneath the closure flap.

Do not force an item into the envelope simply because its face dimensions appear suitable.

If the contents are particularly valuable, thick or close to 229mm x 324mm, request a sample and complete a packing test first.

Protecting Certificates and Important Documents

A4 Board-Backed Envelopes are particularly useful for certificates and important papers that should arrive without fold lines.

Before inserting the document:

• Make sure the ink is completely dry
• Remove loose staples or sharp fasteners
• Place several sheets into a suitable paper folder where necessary
• Use a protective sleeve for delicate surfaces
• Keep the document flat
• Avoid touching photographic or coated surfaces unnecessarily
• Confirm that the envelope is clean and dry

For documents that must remain pristine, consider placing an additional sheet of rigid card on the front side of the contents.

The board backing reduces bending, but additional protection may be appropriate for irreplaceable certificates, original artwork or high-value documents.

Protecting Photographs, Prints and Artwork inside of A4 board backed envelopes

The rigid backing can help protect photographs, illustrations and flat artwork from ordinary bending.

However, photographic and printed surfaces may scratch, scuff or transfer ink when placed directly against kraft paper.

Use a suitable protective sleeve, tissue layer or glassine sheet where required.

Make sure the protective material is:

• Clean
• Dry
• Acid-free where appropriate
• Large enough to cover the printed surface
• Free from loose adhesive
• Suitable for the artwork or photograph

Do not send wet paintings, damp ink, loose charcoal, unset pastel or other materials that could transfer onto the envelope.

Original or valuable artwork may require an archival sleeve, additional rigid boards and a strong postal carton.

Suitable for E-Commerce and Business Mailings

These A4 Board-Backed Envelopes provide a practical option for:

• Online retailers
• Offices
• Accountancy businesses
• Solicitors
• Estate agents
• Educational organisations
• Photographers
• Artists
• Print businesses
• Marketing agencies
• Publishers
• Recruitment companies
• Training providers
• Insurance businesses
• Financial organisations
• Local authorities
• Healthcare administration
• Customer-service departments
• Mail-order companies
• Fulfilment centres

Selling the envelopes individually allows businesses and occasional users to order only the number they require.

This is helpful for one-off documents, occasional certificates, customer replacements, samples and small mailing campaigns.

Individually Sold A4 Board-Backed Envelopes

We sell each 229mm x 324mm A4 Board-Backed Envelope individually.

Individual sales provide flexibility for customers who do not need a complete bulk quantity.

They are particularly useful for:

• One-off document deliveries
• Occasional business correspondence
• Replacement certificates
• Individual photographs or prints
• Customer returns
• Product samples
• Small offices
• Home businesses
• Trial orders
• Testing the envelope before regular use

Enter the total number of individual envelopes required when ordering.

Check the quantity carefully before completing your purchase, as the ordering unit represents one envelope.

Preparing the Envelope for Posting

Place the envelope on a clean, dry and stable surface.

Before packing, inspect:

• The kraft paper front
• The rigid board backing
• Side and bottom seams
• Closure flap
• Adhesive strip
• Release liner
• Printed handling message

Do not use an envelope that appears wet, torn, punctured or heavily creased.

Arrange the papers neatly and align their edges. Insert them carefully without forcing the corners against the seams.

Make sure all contents sit below the opening. Then check the delivery address and enclosed documents before removing the release strip.

Close the flap, press firmly across the adhesive area and apply the delivery label to a flat section of the front.

Finally, measure and weigh the completed item according to the requirements of your chosen delivery service.

Applying Postal and Courier Labels

Position the address or courier label where it remains flat, visible and easy to scan.

Avoid placing important information across:

• The sealing flap
• Side seams
• The bottom seam
• Bent corners
• Creased areas
• The printed handling instruction
• Areas distorted by thick contents

Make sure:

• The recipient’s address is correct
• The postcode is clearly visible
• Barcodes remain smooth
• Old labels are removed or fully covered
• The return address is included where required
• The selected postage is correct
• Tracking labels are firmly attached

The red PLEASE DO NOT BEND wording should remain visible wherever possible.

Always check the current size, thickness and weight limits of the selected postal or courier service before dispatch.

Board-Backed Does Not Mean Completely Bend-Proof

The board helps resist ordinary bending, but it cannot prevent all damage.

Excessive pressure may still bend or crease the envelope. This can occur if the item is:

• Forced into an overfilled mail sack
• Trapped beneath heavier parcels
• Inserted into a narrow letterbox
• Processed through unsuitable machinery
• Dropped or crushed
• Stored in damp conditions
• Folded deliberately
• Packed with insufficient clearance

The printed warning may encourage careful handling, but it does not guarantee that every handler or machine will keep the envelope flat.

Use additional rigid protection whenever bending could cause serious loss or damage.

These Envelopes Are Not Padded

A board-backed envelope provides rigid support but does not contain bubble lining, foam or another cushioning material.

It can help protect papers from bending, but it does not absorb impact in the same way as a bubble-lined mailer.

Do not rely on this envelope alone when sending:

• Glass
• Ceramics
• Electronic devices
• Delicate jewellery
• Fragile components
• Crush-sensitive products
• Heavy metal items
• Products requiring impact protection
• Items with sharp edges
• Liquids

Use suitable cushioning and a rigid postal carton for fragile products.

Water and Weather Resistance of A4 board backed envelopes

The kraft paper and board construction should not be treated as waterproof.

Rain, spills, condensation and prolonged damp conditions may:

• Stain the envelope
• Weaken the paper
• Soften the board backing
• Affect the adhesive
• Damage postal labels
• Cause inks to run
• Reach the enclosed documents
• Distort the envelope

Do not immerse the envelope or leave it outdoors.

Documents requiring moisture protection should first be placed inside a suitable waterproof sleeve or sealed inner bag.

Additionally, choose a delivery and storage method appropriate for the value and sensitivity of the contents.

Products These A4 board backed envelopes Should Not Contain

Do not use these A4 Board-Backed Envelopes as the only packaging for:

• Exposed blades
• Needles
• Sharp metal parts
• Broken glass
• Heavy tools
• Hot items
• Wet products
• Free-flowing liquids
• Leaking containers
• Solvents
• Corrosive chemicals
• Clinical or infectious materials
• Hazardous substances
• Pressurised containers
• Dangerous goods
• Batteries requiring regulated packaging
• Products requiring UN-approved packaging
• Highly fragile items
• Bulky products
• Items prohibited by the chosen delivery service

Sharp, hazardous, liquid, fragile or regulated contents require appropriate specialist packaging.

Opening the A4 board backed envelopes Safely

Recipients should open the envelope carefully to avoid damaging the contents.

Where scissors or another cutting tool are required, cut close to the outer edge and keep the blade away from the enclosed documents.

Senders should leave sufficient clearance between the contents and the opening. This helps reduce the risk of somebody cutting through the papers inside.

The permanent adhesive flap may tear the paper when opened. Therefore, the envelope may not remain suitable for another postal journey.

Remove every document before placing the empty envelope into an appropriate reuse, recycling or disposal route.

Storage Recommendations

Store unused board-backed envelopes flat in a clean and dry indoor area.

Keep them away from:

• Moisture
• Direct sunlight
• Excessive heat
• Naked flames
• Dust
• Grease
• Solvents
• Sharp objects
• Heavy products
• Crushing pressure
• Extreme temperature changes

Do not bend, roll or fold the envelopes during storage.

Stack them evenly on a flat surface and avoid placing heavy items on top. Excessive pressure may crease the kraft paper or permanently distort the board.

Keep the release strip in place until the envelope is ready to use.

Why Choose Our A4 Board-Backed Envelopes?

Our A4 Board-Backed Envelopes combine a practical kraft paper front, supportive rigid backing and convenient peel-and-seal closure.

The 229mm x 324mm dimensions are suitable for standard A4 documents measuring 210mm x 297mm, allowing compatible papers to remain unfolded.

Meanwhile, the board backing helps reduce unwanted bending and creasing during ordinary postal handling.

The red PLEASE DO NOT BEND message provides a clear handling instruction, while the brown paper front offers space for addressing, postage and courier labels.

Because the envelopes are sold individually, customers can order the exact number needed for occasional documents, small mailing projects or trial use.

What Are A4 Board-Backed Envelopes Also Known As?

People may also refer to these products as:

• A4 cardboard-backed envelopes
• A4 rigid envelopes
• A4 hard-backed envelopes
• A4 document mailers
• A4 document envelopes
• A4 postal envelopes
• A4 stiff-backed envelopes
• A4 kraft board envelopes
• A4 do-not-bend envelopes
• A4 certificate envelopes
• A4 photograph mailers
• A4 print envelopes
• A4 rigid mailers
• C4 board-backed envelopes
• C4 cardboard envelopes
• C4 document mailers
• C4 hard-backed envelopes
• Please Do Not Bend envelopes
• Rigid document mailers
• Board-backed postal envelopes

Although people commonly use these names interchangeably, envelopes can differ in dimensions, usable internal capacity, board thickness, paper weight, closure design and rigidity.

Always check the complete specification before ordering.

Food Contact Information

These board-backed envelopes are intended for postal and document applications.

Do not place unpackaged food directly inside them unless the product specification and supporting documentation explicitly confirm direct food-contact suitability.

Paper and board construction alone does not demonstrate compliance with food-contact requirements.

The envelopes may carry food products already protected by suitable sealed primary packaging, provided the contents do not leak, release grease or create condensation.

If you require confirmation for a food-related application or need supporting documentation, please email sales@expresspackaging.co.uk before ordering.

PPWR Compliance Information

Regulation (EU) 2025/40 on Packaging and Packaging Waste, commonly known as the PPWR, applies to packaging placed on the EU market.

We can provide available product specifications and supporting information to help customers complete their compliance assessments. However, paper or board construction and potential recyclability alone do not confirm full PPWR compliance.

The responsible economic operator must assess the finished packaging and its intended use against all applicable requirements, including packaging minimisation, substances of concern, material composition, recycled content, recyclability, labelling and technical documentation.

The current product information does not confirm a particular percentage of recycled content. Therefore, do not make a recycled-content claim without supporting documentation.

Customers intending to place these envelopes on the EU market should email sales@expresspackaging.co.uk to request the latest available documentation before making a recyclability or PPWR compliance claim.

Material and Responsible Disposal

These envelopes combine a kraft paper front, rigid board backing and adhesive closure.

Clean and uncontaminated paper and board packaging may be accepted by paper-recycling services, depending on local requirements.

Before recycling:

• Remove the contents completely
• Remove plastic document sleeves where practical
• Remove incompatible labels where required
• Keep wet or contaminated envelopes out of clean paper recycling
• Follow the instructions of your local authority or commercial waste contractor

Adhesive, coatings, labels and other attached materials may affect acceptance.

Where an envelope remains clean, dry and structurally sound, consider reusing it for suitable internal storage or document protection before disposal.

Important Safety Information

Store unused envelopes in a clean, dry place away from direct heat, naked flames and prolonged sunlight.

Paper and board are combustible. Therefore, do not use or store the envelopes close to open flames, hot surfaces or ignition sources.

Do not overload the envelope or force thick products inside. Excessive pressure may split the seams, distort the board or prevent the flap from sealing correctly.

Protect the paper and board from water, sharp objects and abrasive surfaces.

When using scissors or blades to open the envelope, cut away from the body and enclosed documents.

Keep detached release strips and other small packaging components away from babies and young children.

Always comply with the postal, courier, labelling and transport rules that apply to the intended contents.

Sample Requests

To request a sample, please email sales@expresspackaging.co.uk or call 0121 622 2347.

Our sales team will confirm the sample and delivery arrangements before sending it.

Illustration Only

Documents, certificates, photographs, prints, labels and other items shown in our product images demonstrate potential applications only and are not included with the envelopes.

Products vary in width, height, thickness, shape, rigidity and weight. Therefore, measure the complete prepared item carefully and confirm that it fits comfortably within the 229mm x 324mm envelope.

Product photographs provide a general representation of the kraft paper, rigid backing, adhesive strip and printed warning. Colour, texture, board shade, print position and finish may vary slightly between production batches.