13. Fees payable to the Company’s auditor
| 2022 US$m | 2021 US$m | |
| Audit of the Company and Group financial statements | 1.2 | 0.7 |
| Audit of the financial statements of the Company’s subsidiaries | 5.7 | 4.5 |
| Audit-related assurance services | 0.6 | 0.6 |
| Other assurance services | 0.2 | 0.1 |
| Total fees payable to the Company’s auditor and its associates | 7.7 | 5.9 |
| Summary of fees by nature: | ||
| Fees for audit services | 6.9 | 5.2 |
| Fees for audit-related assurance services | 0.6 | 0.6 |
| Fees for other assurance services | 0.2 | 0.1 |
| 7.7 | 5.9 |
The guidelines covering the use of the Company’s auditor for non-audit services are set out in the Audit Committee report. Fees for other assurance services were capped at 30% (2021: 30%) of the fees for audit services. In the year ended 31 March 2022, fees payable for non-audit services, were 12% (2021: 13%) of fees payable for audit services. Such fees are reported within Other operating charges.
The fees for audit-related assurance services relate to the Group’s half-yearly financial report and US$0.1m (2021: US$0.1m) of the fees for other assurance services was for bond issuance related reports.