Hello I am a lawyer with over 15 years experience. I will try to help you with this. Was this money a gift or a loan?
If it was a gift then I don't think it will be a problem. The only cause for concern I have is your comment that it was "also to pay care fees". Was this explicitly stated by her when she gave you the money or did she give you the money and simply trust you to use your money to help her as necessary. Also when did she make the gift?
I am going to bed now so won't answer again unitl tomorrow morning.
Do you have any siblings who are or are likely to be unhappy with this.?
This will hinge on whether the money was a true gift or was given to you to use to look after her in which case it could be argued you were holding it on trust for her and that it is therefore part of her estate. If your concern is to avoid tax then IHT will be payable on this gift as your mother lived for less than 7 years after making the gift. If your intention is ti retain the money and not share it with your siblings then you could be heading for a messy dispute. If this is the case I would strongly suggest that you instruct a solicitor in the orthodox way as this site will not be able to provide the level and detail of advice that you will need.
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