Interested in thoughts on keeping the integrity of historical data

Hello hollyylloh,

I guess I would say it this way. You really haven't told us what your exact
needs are for storing historical data. If your answer is "everything", such
is a big task, and probalby broader than needed.

In my response I was trying to "read between the lines" and guess at the
answer that you didn't give us. You described a very common need/ problem
which is that most Access db's that handle "invoicing" don't treat invoices
as entities to be stored. They treat it as something that is "derived" from
other data (only) at the time of printing. This cause the type of problems
that you describe. You want to look at an old invoice as sent, and
sometimes it no longer possible to do so. Because some of the data has
changed.

If that is the issue, and if it is enough of a problem to be worth some
extra complexity to solve, that would be to consider an invoice to be an
item(entity) that is created and stored (separately from the data that it
was derived from) at the time of invoicing.