Thanks for your question - I am Sam and I am one of the UK tax experts here on Just Answer.
Yes you will be liable to capital gains tax as you are selling a UK share of propriety (so in essence are also selling your share of the partnership which remains liable to UK tax inspire of you residency status)
Yes you are, as already advised above (you are liable in spite of your residency status)
If you were exempt due to your residency/non domicile I would have stated this
You are not selling commercial property per se you are selling your share in the partnership which happens to link in with the property - so you are liable to tax on this sale as advised.
You advsie this is partnership in a trade rather than just owners of a commercial property that receives rents - so can you clarify the exact position by answering the following questions as I feel we are just going around in circles and you are providing me no further information for me to have a different answer for you which you see to want.
Is it one commercial property or several
Does the partnership trade in business and use this commercial property in trade or rent it out and just receive rents
What income do you receive on which you suffer UK tax
Then its not a partnership (trade income) its just rental income
And in that instance your accountant is correct there is no capital gains to pay in the UK as its a commercial rental, but you should declare this gain in Spain