What the 2026 rules change for mid-caps

What actually changed

The 2026 package is being sold as a rewrite. It is not. Three of its four parts restate what large filers were already doing; the fourth lowers the threshold, which is the part that matters if you are between two hundred and a thousand people and have never filed before.

The practical change is not the disclosure. It is that the numbers behind the disclosure now have to survive someone else reading them, in a year when your own finance team is seeing them for the first time.

The threshold moved, the burden did not

A mid-cap filing under the new threshold carries the same evidence requirement as a large one. There is no light-touch tier. What changes is how much of it you already have lying about.

• Scope 1 and 2 are a metering exercise, and most firms pass on the first try.
• Scope 3 is where the year goes, and category 1 alone is usually half of it.
• The boundary has to be written down before anything is counted.
• Prior-year comparatives are expected, which means measuring 2025 as well.

What your auditor asks for first

Not the total. They ask for the boundary note, then for one figure chosen at random and the file it came from. If that file has a name, a date and a person attached to it, the rest of the conversation is short.

Agree the boundary and write it down. Pull one month of meter data and reconcile it against the purchase ledger; whatever gap appears there will appear across the year.

What to do before March

Three things, in this order. Settle the boundary and have somebody sign it. Reconcile a single month of meter data against the ledger, because whatever gap shows up there will show up across the year. Then decide which parts of Scope 3 you will measure and which you will label as an estimate — and say which is which in the body of the report, not in a footnote.