Can you tell me how much the current mortgage is and what will be owing after you have remortgaged? I'm assuming it will be £310,000 but it's worth checking.
Take a look here for information on the transfer of equity and stamp duty and here for the current rates.
Assuming you will own a 50% share and you are taking on 50% of the mortgage, the stamp duty charge will be £600 (£310,000 / 2 - £125,000 x 2%).
I hope this helps but let me know if youi have any further questions.
I am looking at the rules for increased stamp duty for second property purchases to see if the 3% additional stamp duty will apply to you. If it does that will add £4,650 to your stamp duty bill to make it £5,250 (£125,000 @ 3% + £30,000 @ 5%). Whilst you will be taking an interest in a second property, it's not a purchase in the strict sense in my view. I will get back to you on this.
If you get your name on the deeds before you remortgage, you will be taking on £44,500 of mortgage which may incur a 3% stamp duty charge of £1,335 as the transfer is over £40,000. Once your name is ***** ***** deeds, you can remortgage and pay no stamp duty as there will be no transfer. You will both be on an equal footing as you apply for the remortgage.
I will be back in about 30 minutes.
You can do it yourself if you wish. Look here for further information.