Reconciliation

First step:  find all allowed combinations on either side.  Here's the sample code for the Bank table (five items).  For later reference to the values an index column is added as a convenience (not strictly required)

Bank table

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WcjJU0lEyNNM3MNU3MjAyAXEMlGJ1gBJGQLaRCZKECVTCGCRhgSRhBpUAsY0NsUiYgnTrG5jBrTBRio0FAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, Date = _t, Value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Value", Currency.Type}, {"Date", type date}},"en-GB"),
    #"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 0, 1, Int64.Type)
in
    #"Added Index"

Combine function to find and deduplicate combinations

(tablea,listb)=>
let 
    Next = Table.AddColumn(tablea,"id",each listb),
    #"Expanded id" = Table.ExpandListColumn(Next, "id"),
    #"Replaced Value1" = Table.ReplaceValue(#"Expanded id",each [ID],each List.Sort(List.Distinct([ID] & {[id]})),Replacer.ReplaceValue,{"ID"})
in 
    Table.Distinct(Table.SelectColumns(#"Replaced Value1",{"ID"}))

Final result for combinations of five items based on the Bank table

let
    Source = List.Accumulate({1..Table.RowCount(Bank)-1},Table.FromList(List.Split(Bank[Index],1), Splitter.SplitByNothing(), {"ID"}),(state,current)=>Combine(state,Bank[Index])),
    #"Extracted Values" = Table.TransformColumns(Source, {"ID", each Text.Combine(List.Transform(_, Text.From), ","), type text})
in
    #"Extracted Values"

Then you can lookup the sum value for all these combinations, repeat the process for the seven items of the Financials table, and the do yet another cartesian to match the sums.