Hi RJMC13,
For tax purposes, by default, a husband and wife and civil partners, split the income / capital gain is split 50:50.
For HMRC agreement to alter this split, to apply the beneficial ownership ratio, a form 17 must be submitted to HMRC including a copy of the declaration, within 60 days of the form 17 being signed.
If you did not do this prior to disposing of the property, then Capital Gains Tax liability must be calculated at 50:50 split.
Please have a look at:
Declare beneficial interests in joint property and income
And
TSEM9862 - Property held jointly by married couples or civil partners: Form 17 rule - strict time limit
If you did submit a form 17 and it was formally agreed by HMRC, you will need to work out if your HMRC agreed share results in a capital gain.
If it does, you will need to report your gain within 60 days of the disposal date.
If you have no Capital Gains Tax to pay, you do not need to report the property disposal.
Thank you.