Large companies Due dates

For companies with the normal 12 month accounting period – see OT study notes chapter 23, section 1.3, p.123.

If the accounting period is less than 12 months then:

The amount of each instalment:

= (estimated CT liability for AP) × (n/length of AP)

Where n = 3 months for a full quarterly instalment
But n = 2 or 1 for the last instalment if the period since the previous
instalment is less than 3 months

Example
A large company prepares accounts for the 8 months to 31/12/20 for which the estimated CT liability is £800,000.

1st Instalment = 14th day of 7th month from start of AP = 14/11/20
Amount = 3/8 x 800,000 = 300,000

2nd Instalment (3 months later) = 14th day of 10th month from start of AP = 14/02/21
Amount = 3/8 x 800,000 = 300,000

NOTE – the final instalment date is always 4 months (14th day of) after the end of the AP – which in this example would be 14 April 2021

As this is only 2 months after the previous instalment date the 3rd and now final instalment will be –
Amount = 2/8 x 800,000 = 200,000

For an accounting period of 3 months or less applying the above instalment rules would result in the date of the first instalment being later than the last instalment. Therefore, in this situation the full tax due for the accounting period is due on the date of the last instalment, i.e.14th day of 4th month after the end of the accounting period.

(You should be able to find these details in whichever study manual you may be using – but you might see now why I left this out of our study notes!)