GekiPDF

Merge PDFs for HMRC Self Assessment: Keep Accounts Under the 5 MB Limit

Combine up to 20 PDF files into one attachment for HMRC online filing. No signup, no watermark, files deleted after an hour.

    Runs the same engine as our Merge PDF tool.

    HMRC's online self-assessment service accepts PDF attachments up to 5 MB. If your accounts span multiple pages or separate documents, you need one file that fits under that ceiling. GekiPDF lets you merge up to 20 PDFs in a single run, so you can combine your tax return, profit and loss statement, and receipts into one attachment without re-encoding pages.

    Drag your files into the browser window to reorder them — the first page of the merged PDF will be the top of your first document. Pages are copied losslessly, meaning text stays selectable and mixed page sizes (A4, A3, or scanned letter) are kept as-is. Files up to 50 MB each are accepted, and you get 40 conversions per hour per IP. No signup needed; your uploads are deleted after one hour.

    Frequently asked questions

    What is the maximum file size for HMRC self-assessment attachments?

    HMRC's online filing typically allows PDF attachments up to 5 MB. Merging multiple PDFs with GekiPDF keeps total size under this limit if original files are small enough.

    Can I reorder pages before merging for my tax accounts?

    Yes. Drag and drop each uploaded file in the list to set the order. The final PDF will follow that sequence exactly.

    Will merging reduce the quality of my scanned accounts?

    No. GekiPDF copies pages without re-encoding them. Text remains searchable, and image resolution stays unchanged.

    Do it in the full tool

    Open Merge PDF for all options, or jump straight to another step below.

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