It is not necessary to attach the bank statement to the tax return. However, in case of doubt, the tax officer may request it. Amounts paid by standing order, direct debit, or online banking are recognised in conjunction with the bank statement. Cash payments are not recognised.
The condition of bank transfer still applies. Invoices paid in cash will not be recognised.
If you do not yet have a current service charge statement or a separate certificate according to § 35 a EStG for 2021 from your property management, this is not a problem. It is permissible to claim the total expenses for the tax year in which the statement is received by the tenant. You therefore take the most recent service charge statement you have – presumably from 2020 – and claim these costs in the tax year 2021. All tenants and property owners who have not yet received the current certificate according to § 35 a EStG for 2021 can proceed in this way!
All private individuals who have commissioned tradesmen or service providers claim the expenses in the tax year in which they paid the corresponding invoice themselves.
Note: In 2019, the Federal Fiscal Court unfortunately ruled against the generous stance of the tax authorities that the tax reduction according to § 35a EStG for household-related services is only granted for expenses incurred by a taxpayer for their own accommodation in a home or for their own care. However, the tax benefit is excluded for expenses incurred for another person, i.e. if children cover the costs for their parents (BFH ruling of 03.04.2019, VI R 19/17).
The tax authorities are now applying the ruling!
Currently, the Berlin-Brandenburg Fiscal Court has also dealt with the assumption of care costs for a parent. According to this, § 35a EStG favours – if at all – only expenses for the outpatient care of relatives in the taxpayer's own household (i.e. the carer's), but not for the outpatient care of relatives in their household (ruling of 11.12.2019, 3 K 3210/19). HOWEVER: An appeal was explicitly allowed, which has since been filed (Ref. VI R 2/20). The BFH will therefore have to address the issue of the assumption of care costs again.