Three dates most calculators get wrong
Each of these is a rule that looks like another rule, which is exactly why published calendars keep repeating them.
- OPC AOC-4 is 180 days, not six months. From a 31 March close that is 27 September. Plenty of tools show 30 September.
- LLP Form 8 anchors twice. Six months to 30 September, then 30 days — 30 October. Treating it as seven months from year-end gives the wrong day.
- A company incorporated in January starts a 15-month first year. Under section 2(41), incorporation on or after 1 January means the first financial year ends on 31 March of the following year — which shifts every first-year deadline.
Once you have your dates, each form has a plain-language guide explaining what it is, what it costs and what happens if it slips — start from the FY 2025-26 calendar.

