Like Maxine, I am not sure precisely what it is that you, Samina, wish to achieve.
However, you may wish to consider constructing your Distribution account including 4 columns ie Narrative, Gross, IHT and Net.
Balance brought forward from Accounts shown under Net column [and so also Gross]
Add back IHT [&interest] under IHT, with total carried to Gross.
For each individual beneficiary then show “Notional” grossed-up legacy [under Gross column] less IHT [& interest] attributable [as negative under IHT column] leaving net legacy under Net column [which should then be one-ninth].
For each charitable beneficiary simply show Net legacy under both Gross and Net columns [being the same figure which should also be one-ninth].
All three columns should then total Nil.
However, the IHT liability was based on values at date of death [and may be affected by other factors such as IV gifts and/or associated trusts], whereas the final estate accounts should include administration costs and expenses; capital gains and losses and administration income. So the “adjusted” accounts may give a lay beneficiary an idea yet he/she may still need some narrative explanation as to how the tax was actually calculated.