When BAS Dec-2020 was compiled on 29th Jan, that would’ve been the GST on Sales value. When compiling the BAS, there are several moving parts therefore we take a step by step approach to check account balances and to spot obvious errors. It’s only during a full bookkeeping review, which looks at the last 6 month’s transactions, that coding inconsistencies will be identified.
Your monthly bookkeeping review was done on 1st Feb. I found a GST On Income line that should’ve been GST Free Income so I recoded it. If I feel that the edit makes a significant difference to a lodged BAS, I’ll advise the client and revise. At the end of the financial year, the tax agent will run a full 12 month BAS and GST Reconciliation to compare with what has been lodged each quarter. Any differences will be adjusted, including adjustments made as part of preparing the company tax return.
No matter how vigilant we might be, the nature of bookkeeping is that there are always tweaks, back dated items, late items and mis timings. We don’t “lock” Xero at every reporting point but let it flow with what we have at the time knowing that it’ll be caught and corrected eventually.