Here is a list of factors that need to be considered when calculating basic earnings per share (EPS) under IAS 33, as well as the adjustments that may need to be made to the calculation:

1. Net income: The net income for the period needs to be divided by the weighted average number of ordinary shares outstanding during the period to calculate basic EPS.
2. Weighted average number of ordinary shares outstanding: The weighted average number of ordinary shares outstanding needs to be calculated based on the number of shares outstanding during each period and the amount of time they were outstanding.
3. Stock splits and bonus issues: If there are any stock splits or bonus issues during the period, the number of shares outstanding needs to be adjusted accordingly to calculate the weighted average number of ordinary shares outstanding.
4. Treasury shares: Treasury shares, which are shares that a company repurchases and holds in its own treasury, should be excluded from the calculation of the weighted average number of ordinary shares outstanding.
5. Share-based payments: If a company issues share-based payments, such as stock options or restricted stock, the impact of these payments on the calculation of basic EPS should be considered. The cost of these payments should be recognized in the income statement and included in the calculation of net income.
6. Convertible securities: Convertible securities, such as convertible bonds or preferred stock, may have a dilutive effect on EPS if they are converted into ordinary shares. The impact of these securities should be considered when calculating basic EPS.
7. Dilutive potential ordinary shares: Dilutive potential ordinary shares, such as stock options or convertible bonds, should be included in the calculation of diluted EPS. However, they should be excluded from the calculation of basic EPS.

Overall, when calculating basic EPS under IAS 33, companies need to consider a range of factors, including net income, the weighted average number of ordinary shares outstanding, stock splits and bonus issues, treasury shares, share-based payments, and convertible securities. By carefully considering these factors and making appropriate adjustments to the calculation, companies can provide accurate and reliable EPS information to investors and other stakeholders.