7 Property operating expenses
| | 2016 | 2015 |
Taxes | 7,669 | 7,419 |
Insurance | 162 | 184 |
Maintenance | 23,276 | 18,961 |
Valuation fees | 748 | 395 |
Property management fees | 3,136 | 2,966 |
Promotion and marketing | 436 | 792 |
Letting and lease renewal fees | 4,958 | 4,001 |
Other operating expenses | 6,852 | 5,481 |
Addition to provision for bad debts | 493 | 815 |
Total property operating expenses | 47,730 | 41,014 |
In 2016, € 0.5 million (2015: € 0.5 million) of the maintenance expenses related to unlet properties.