SDLT on additional share of BTL

[pknight]

Hi, I’m hoping someone can help with the following query as I’m not convinced my solicitor is correct

I’m buying my brothers 1/3 share in a BTL in which I already own 1/3 of it (we both have other BTLs so are familiar with the 3% additional SDLT) - the property is worth £100k and the outstanding mortgage is approx £55k, so his 1/3 share is worth £15k, which I am paying

He is also being released from his 1/3 share of the mortgage, approx £18.33k

Therefore the total consideration is the £15k I’m paying in cash, and the £18.33k of mortgage debt he’s being released from, so £33.33k total

My solicitor believes I’ll be liable for 3% SDLT on the £33.33k, but I believe I won’t be liable for any stamp duty cos the total consideration is below £40k

Who is correct?

Many many thanks for any responses
Paul
ps - I’m a qualified chartered accountant and have read the legislation in this area but cannot seem to make sense of it with respect to my scenario