CAT

[Mandy29]

I recently received an inheritance of 40k euro from my late partners mother who was ROI nationality My partner died over 20 years ago and we had a son together. I am a UK national and resident. The solicitors seem to have missed the fact that CAT was due. My understanding is that as we were unmarried my relationship to his mother means maximum CAT is due even as the mother of her grandchild albeit 25 years old now.
Is there any exemption in my situation or alternatively can I chose to pay tax in UK where relationship has no bearing in this circumstance and no tax would be due.
An early reply of thoughts would be much appreciated as only jus found out about this in last week