I don't know if I would say that I integrate any particular software into my GTD System. Integration encompasses a large swath of possibilities and complexities, many of which are littered with pitfalls and caveats. Rather they are just tools to do my work much like a spreadsheet, word processor, or web browser. I find it helpful to think in terms of larger styles/chunks of work instead in terms of tools, locations, people, or processes. However, that's just one style.
For example, I would have a "Financial Management" list that would contain those types of tasks. I may need to use various software applications to complete any given task on that list (e.g. web browser, email client, pdf's/files, etc.) but it's easier to batch handle them all at the same time ... thus the list. That's just one way to do it though.
Most of the time, accounting tasks have firm deadlines (i.e. invoices filed by certain dates and/or times, accounting records updated as part of closing out the previous month in the first days of a new month, etc.), so a good chunk of them end up on my calendar for the various days they are due. Since these are non-negotiable tasks, they get priority and a place on my calendar to get done. Otherwise I would time block specific parts of my day as "Work off of Financial Management list" to keep that list small and empty, if possible.
I could keep them all in a task manager or list manager, however, I classify those as "tasks to be done as soon as I can" rather than "tasks that MUST be completed on a specific date and/or time". I do, however, keep a checklist with various steps for such routine tasks in my task manager but it's purely reference and not an action reminder for me.
In a weekly review, you could add an entry for "Get current on accounting tasks". Whereby you would go process and organize whatever specific software contains those items (e.g. run reports, check records, verify books, etc.) or reference your checklist to make sure that everything is as current as possible on a week-by-week basis (e.g. invoices filed, collections sent, records updated, etc.) so that closing is ideally less effort.
In essence, your lists are pointers to your accounting software whereby the more specialized work happens and is tracked accordingly. You may have reference checklists and/or materials that are action support for such tasks in your GTD System, but that would be about the extent of it.
For items that come up, such as "E-mail Ricky about discount to apply to invoice #ABC-123", you could put those on your lists as needed. Then when you do reconciliation or processing of your "Financial Management" list (i.e. that task would be on this list since it's focused around this chunk of work but again, that's just one way to do things) you could check those items and handle accordingly.
Trying to force GTD into an accounting application like Dynamics or QuickBooks is ill-advised as it is like trying to use a plane as a boat.
