Submitting plans online: file formats, scale and what goes wrong

PDF is the expected format for drawings. It carries a defined page size, so the receiving system knows the sheet is A4 and the stated scale means something.

A JPG or PNG has pixels but no paper size. Uploaded as a drawing it can be printed at any size, which makes the stated scale unverifiable — and it usually looks worse too. Where a photograph or a site image is genuinely wanted, an image file is fine; for a scaled plan it is not.

Each drawing should be a separate file, named for what it is, because the case officer and any consultees look at them individually rather than as a bundle.

Names like "Location plan 1:1250 A4" or "Proposed elevations" are self-explanatory a year later, when a condition is being discharged and someone is trying to work out which drawing the permission referred to. "scan001.pdf" is not.

Many authorities ask that each drawing carry a drawing number and revision on the sheet itself, so that the permission can refer to it precisely. If yours does, put it in the title block rather than only in the filename.

This is where correct drawings go wrong. When exporting or printing to PDF, the page size must match the sheet the drawing was made for, and the scaling must be set to none — 100%, actual size, or however the application words it.

Anything described as "fit", "shrink to fit", "scale to fit printable area" or "auto-rotate and centre" can resize the drawing. The result looks correct on screen and measures wrong on paper, which is exactly the failure a scale bar is designed to catch.

After exporting, it is worth checking: open the PDF, measure a known distance against the scale bar, and confirm it reads what it should.

Upload systems impose limits on file size and sometimes on the number of files. Limits differ between the national portal and individual authority systems, and they change — check the current guidance on whichever system you are using rather than trusting a figure you read elsewhere.

If a drawing is too large, the fix is to export it at a sensible resolution rather than to compress it until the linework blurs. A plan that cannot be read at full zoom will be queried.

Paper submission still exists, and some authorities still ask for printed copies for site meetings, committee packs or consultees. If you are printing, print at 100% and check the scale bar on the printed sheet, not on screen.

Ordnance Survey mapping supplied under a licence carries a limit on how many copies may be printed. That limit is stated with the plan when you buy it, and printing beyond it is a licensing matter rather than a planning one.