As a general rule, you can. You must ensure you come back to the scheme within 11 months of the last voucher entry and have not joined the TFC Scheme or changed employer. This is with the exception of contracts that don't allow this (as specified in your company handbook).
You leave the scheme in January ready for January payroll. This means your last actual voucher was December. You must have a payroll deduction and voucher credited to your account by November to be able to re-join.
You leave the scheme in January but miss the cut off, your last voucher is in January and February is your first month without a voucher. This means you must have a payroll deduction and voucher credited to your account by December to remain in the scheme.