Can we profit from any errors in GP payments?
There can be few practices that have not found errors in their NHS payments. The complexities of the current GP payment system make these inevitable. Once you have become aware of the mistake you are obliged to report the fact. Your accountants, in their auditing capacity, are equally obliged to do so if you do not.
There are several ways to look at this. An error in your favour means the extra you have been paid is public money not yours.
If the error had been the other way around you certainly would have expected to get the money back, and quickly.
Your accountants are also obliged to show this overpayment in your written accounts, which in turn are seen by the Inland Revenue. You have had the benefit of the extra cash-flow for probably several months as the error occurred last financial year and your accounts have probably taken at least another six months to prepare.
If you had failed to report the overpayment, the error would probably have come to light in the future in any case.
Even if you ignore the above, the most powerful point is if you now knowingly keep this money you could be accused of fraud with all the consequences that would follow.
Bite the bullet and own up. Your honesty may at least help you persuade the powers that be to spread the deduction over more than one quarter.