Genie Gill

Both parents died weeks apart. Reading the inheritance tax guide, since they were joint homeowners I know that mum inherited dad's tax allowance and so we have a double threshold. We need to apply for probate from mum as she died last. Working out the gifting is causing confusion. The annual £3000 limit, does this mean we add up over the year gifts and see if it's over £3000 or is it single gifts of £3000 or more? What about gifts from joint account years ago, do we half the amount as it was from both of them and see if its less than £3000? Do we count gifts up first for each tax year followed by the value of the house to see if we pay inheritance tax?