Simply Accounting: "you can no longer open it with the Basic version
This warning means converting your Simply Accounting data up to Premium is permanent: the file will not open in Basic afterwards.
When Simply Accounting shows “Once Simply Accounting converts your data to the Premium version, you can no longer open it with the Basic version,” it is issuing a warning, not reporting an error. The program is about to rewrite your company data so it matches the Premium edition, and it is telling you that the step is permanent: after the conversion, the Basic edition will refuse to open the data. Nothing is damaged at this point; you are simply being asked to accept a one-way change before anything happens.
Why the change cannot be undone in the program
Each edition of Simply Accounting (sold in recent years as Sage 50 in Canada) stores company data in a layout matched to its own features. When the Premium edition converts your data, it rewrites that internal layout to include everything Premium supports. Basic has no way to read the rewritten layout, so it stops at the door. There is no setting, import, or repair command inside either edition that converts the data back down.
If you have not converted yet: back up first
If the message is still on screen, the safest move is to stop and take a complete backup before agreeing to anything. Use the backup facility in Simply Accounting, or close the program and copy the entire folder that holds your company data to a safe location. That copy stays in Basic format and remains openable in Basic, so it is your one native way back. Also check who else uses the file: if any computer in the office still runs Basic, it will be locked out of the data after the conversion.
If you already converted: look for a pre-conversion backup
If the conversion has already happened, check whether a backup exists from before it. Restoring such a backup returns the data to Basic format, but it also returns it to that date, so anything entered in Premium afterwards would have to be re-entered by hand. Whether that is worthwhile depends on how much work has been done since and on the file itself.
If there is no backup: the file needs professional attention
We want to be plain about this: with no pre-conversion backup, there is no do-it-yourself route back to Basic. Rebuilding Premium data into the older edition’s format is a data-engineering job, because every part of the file has to be re-expressed in the layout Basic expects. Our engineers handle this kind of Sage edition downgrade regularly, and a free evaluation of your file will tell you exactly what is possible before you decide anything.
If the real goal is to change products
Sometimes the search for a way back is really a wish to leave the old setup behind. If that is the situation, the converted data can be taken across to QuickBooks instead, with lists and transaction history intact; our Simply Accounting to QuickBooks conversion service covers what carries over and how a Premium-format file is handled.
Next step
Work out which situation you are in: the message is still on screen, you have a backup in hand, or the data is already converted with no backup. The first two are covered above. For the third, get the file evaluated before spending more time on it: a free review will confirm whether a return to Basic is feasible, and you will receive a no-obligation quote for the work.