Sales Tax and Invoicing code overwrites existing CiviCRM invoice ID

See the corresponding wiki entry here for more details:

https://wiki.civicrm.org/confluence/display/CRM/2017+issues+with+Sales+Tax+%28like+VAT%29+and+PDF+Sales+Tax+Invoices

When the (core) CiviCRM Tax and Invoicing code "prints" an invoice for a contact (i.e. a PDF invoice is created for print or mail), after generating the pdf it overwrites the invoice_id field of the contribution table and replaces it with it's new human-readable invoice id, in the form of INV_($contributionID).

This breaks the ability of some payment processors to properly reconcile payments.

As an example, iATS payments makes use of the invoice id to confirm ACH/EFT payments - if the invoice id in CiviCRM is changed, those payments will always stay as pending.

See this post for another example: http://civicrm.stackexchange.com/questions/8840/confusion-between-contribution-id-vs-invoice-id-in-the-database