Thank you for your question. It depends on the agreement you had with your son and daughter in law. If they agreed to pay all sums due in respect of the bank loan you took out for them then they can be liable to pay you interest. On the other hand if you agreed to lend them £12000 and they paid you back and there was never any mention of interest then they don't have to pay you interest. You have to cast your mind back to what was agreed. I hope that helps. Please leave a positive rating so that I am credited for my time.
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