If you are required to submit quarterly VAT returns then October is again a return month. The VAT return must be submitted before the end of October and if there is VAT payable then this must be paid before month end.
Correction of previous periods
If you discover that you have accidentally paid or received too little or too much VAT in a previous period then this must be corrected. If the correction is under € 1,000 then the correction may be made in the tax return. If the correction is above € 1,000, then a supplementary tax return must be submitted containing the correction of previous tax returns.
VAT payable balance check
Recently the tax authorities have announced they will do stricter checks on VAT payable which is included in the balance sheet. If there is VAT on the balance sheet, then the tax authorities can request these to be paid and impose fines.
Yearend
With the yearend bookkeeping a final settlement of the VAT for the year takes place. Too much or too little VAT may have been deducted during the year causing the € 1,000 limit to be exceeded.
Avoid unexpected surprises
It is a good idea to check your VAT in the previous periods to check if too much or too little VAT was deducted. If you may exceed the € 1,000 threshold then it is advisable to correct this in the third quarter VAT return. This avoids you being required to submit a supplementary VAT return at the end of the year.
If you must file VAT returns monthly, then of course you also should check if you are already near the € 1,000 threshold. Prevention is the best cure.