Mutual funds send out a notification of their planned date for a dividend. Some funds issue dividends quarterly, and others have a different schedule. Especially in the last month of the year, it's worth checking the date of the dividend (the dividend date).
To keep things simple, if you purchase a fund after the day it issues the dividend, you can't receive the dividend. If you want to push things a little further, I think the day before the dividend is issued is called the "ex-dividend date". You might be able to buy the day before the dividend and not receive the dividend - but I haven't tested this myself.
Think of this as selecting from two possible scenarios, where it's assumed the stock price doesn't move:
a $20/share asset will issue a $5 dividend. You buy one share for $20, and then receive a $5 dividend. The stock is now $15/share, and you use your $5 dividend to buy 0.33 shares. You own 1.33 shares, and owe tax on a $5 dividend.
Or, you wait for everyone else to get their dividends, then you buy. You spend $20 on an asset that costs $15/share, so you buy 1.33 shares. You own 1.33 shares, and do not owe any tax.