45-day consultation
The 100+ trigger
TULRCA 1992 s.188(1A) sets the 45-day minimum where 100 or more redundancies are proposed. The cut from 90 days came in via the Trade Union and Labour Relations (Consolidation) Act 1992 (Amendment) Order 2013 (SI 2013/763).
Counting the 100
The 100 is counted per establishment, not per legal entity. After the Court of Justice ruling in USDAW v Ethel Austin, "establishment" is the local unit of organisation (a single store, a single office), not the company as a whole. This means a national redundancy programme of 500 spread across 30 small offices may not trigger collective consultation at all if no single site reaches 20.
Protective award exposure
If the employer fails to consult for 45 days, the protective-award exposure is the same as for the 30-day rule: up to 90 days' gross pay per affected employee, set punitively. With 100+ employees, the total liability can be very large; tribunals routinely award the full 90 days when breach is wilful.