Hi Karen,
You can go directly to Ledger 9.0C. You do not have to install every upgrade versin in between. A significant data conversion will be necessary coming from 8.1A, mostly to allow the soft year end. Ensure you have an appropriate amount of time to do this.
The order of upgrading Payables and Ledger does not really matter. You can choose the program you are most ready to upgrade to go first. There are a couple of integration options within Payables that depend on the Ledger version, so you just need to be aware of this after installing the Ledger update and converting the data.
What problems did you hear about with AR/Invoices addresses?
In general, if you are coming from AR version 8.1 or earlier, the addresses could be converted to a 'formatted' layout to allow merging the city, state and zip code into a single field on forms, and also to allow entry of city and state into specific fields (not just an address line). If you are unsure about this, try the AR90 data conversion with a copy of your data before doing it for real. Then you can see how the addresses get converted and if you are happy with this. The address conversion is optional, and you can do it later (via Import Customers) is you wish.
We don't think there are any problems you need to fear about. But the data conversion for GL and AR will require some preparation before starting. If you are unsure, try it with a copy of the data local before doing it for real. You can have both 8.1A and 9.0 versions of GL and AR and Invoices programs simultaneously, to assist with 'testing' the data conversion with a copy of your data, while still working with your live data.
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Regards,
Softrak Tech Support