An 'Estate Credit' will comprise some combination of the following assets: ISAs, VCTs and cash. ISAs and VCTs (the deceased's share, if jointly-held) will not be passed to a spouse, or other beneficiary 'in specie', but will first be liquidated - and 'credited' to the deceased's Estate. Cash, which is 'liquid' by definition, also gets 'credited' to the deceased's Estate - the 'Estate Credit', then, will be the sum total of these assets (as applicable) at the time of death.
General 'unwrapped' investment accounts also form part of a deceased's estate, but these will be 'transferred' directly 'in specie' to a legal spouse (by default), since there are no immediate IHT consequences that might necessitate liquidation of part, or all of the portfolio. If the desired beneficiary of the unwrapped investment is anyone other than a legal spouse, however, then this asset also will be liquidated and 'credited' to the Estate, thereby forming part of the 'Estate Credit'.
By the same token, all 'credits' to the Estate will, in turn, comprise the corresponding 'Estate Distribution'; the mechanism by which these liquid assets will be paid to the intended beneficiary(s).