Hi VOT,
The import VAT should always be recovered during the period in which the import VAT was incurred based on the C 79 evidence.
However, if this has not been done then you can treat this as an error correction and if the value of the import VAT is under £10k then you can include this on the Q4 return.
If the value is over £10K then you would need to send us a VAT 652 to correct this.
Please see the guidance here:
Correcting VAT errors on a return already submitted
Thank you.