Revised Standard Version has a paragraph break here since a new enemy of David is introduced.

And he defeated Moab is literally “And he struck Moab.” Since this clause follows the statement in verse 1 that David had defeated the Philistines, Good News Translation, New Jerusalem Bible, and Bible en français courant say “He also defeated the Moabites.”

And the Moabites became servants to David: This does not mean that the Moabites worked in David’s palace as servants. Rather, they lived under the rule and authority of David and his kingdom (see also verse 6).

And brought tribute: Since this was not a one-time affair, it may be better to say “and started bringing gifts.” Commentators observe that the tribute may have consisted of sheep and wool (compare 2 Kgs 3.4) rather than money, which would probably be implied by the Good News Translation rendering “taxes” and is clearly stated in New Living Translation‘s rendering “tribute money.” So it may be better to render this clause as “and regularly brought gifts” or “and gave him what he demanded.” When one kingdom became subservient to a more powerful kingdom and paid tribute, the weaker kingdom became a vassal. For this reason New Jewish Publication Society’s Tanakh renders the last two clauses of this verse as “the Moabites became tributary vassals of David.” Compare also “and the Moabites became David’s tribute-paying subjects” (American Bible).

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Chronicles, Volume 1. (UBS Helps for Translators). Miami: UBS, 2014. For this and other handbooks for translators see here .