I assume permits pulled before 1991 aren’t on electronic record.

But, for instance, I sent them a notice of rent increase effective February 1 and needed them to confirm that they have accepted the new payment terms through our electronic payment system, and even after repeated notices, they are not responding.

Note this calculation gets worse if you recognize the declining value of currency.  

This will happen in a market with balanced supply and demand, in a monetary system like the US, with fiat currency targeting 2% inflation.- In some markets, that are growing quickly, with great jobs and lots of inbound migration, this could be a little higher - like 4-5% per year over long time periods as demand outpaces supply.

There are quite a few solutions out there so that even the most tech challenged person can pay electronically.

. ;)Preference is electronic transfer through my management software.

As world economics and geo politics have become more of a constant, this Teak investment will serve for diversification in asset class, maturity- since you don't have to harvest, currency arbitrage since main customers are China/India/Europe. 

China manipulates there currency and the situation to gain from such trade imbalance.

I use the Rent Redi software to manage my tenants, so everything is done electronically.

Your GC must sign the contract electronically before a permit can be issued.