dad wants to be partner on a investment property How to add his name on title deeds

Only way to do this is to lodge a Transfer document with a change of name.

In saying this I would be very careful in doing so as it will trigger a Stamp Duty payment as well as possibly a Capital Gains issue. You will also require the consent of the lender who will probably want to reassess the deal given your father will be a prty to the loan and will want to consider his income, asset & liability position.

There are easier cleaner ways for him to be involved so think carefully before you go down this route.

Try a Joint Venture agreement, which basically sets him up as a partner to the investment and you can then nominate whether it's a 50-50 split, 60-40 split of profits and costs etc.  Talk to a solicitor who knows this sort of stuff and they could draft an agreement for you.  As far as the titles office and your lender is conerned, the title will still be in your name, but the JV agreement (which you have no obligation to tell the titles office or your lender about) then brings your dad in on the investment, so there is no stamp duty trigger etc…

This JV agreement as previously stated make you and your dad partners in the investment.  Therefore, if for example you worked it on a 50-5 split, if the property were to make a loss, you and your father would share that loss equally, as is written into the contract.  If it made a profit, you would share the profit – including the capital gain when time comes to sell.  This is all done at tax time.  When the partnership return is done, the income is allocated 50-50 to each of you and you then claim the income (or loss) on your individual personal tax returns.