The refund is a timed bet, not a rebate. It is calculated from your last completed vendor purchase - the gap between that buy and what you earned after it, times 0.9. The window lasts about 20 score ticks (roughly 7-8 minutes). After that, or after you die, the refund is gone even if the vehicle survives.

1How the Refund Actually Works

RuleWhat it means for your tank / heli
Last purchase onlyThe refund recalculates from your most recent vendor buy. Earlier vehicles bought this life are already sunk.
Gap × 0.9Example: $10,000 loadout buy, $6,000 earned after it → $4,000 gap → $3,600 refund. Earn more after buying and the refund shrinks.
20-tick limitA purchase is refundable for ~20 score ticks (ticks land every ~22 seconds, so about 7-8 minutes). Past tick 20 it returns nothing.
Ammo never refundsShells, rockets, and reloads are always sunk cost. Load the minimum for the last push.
Death resets itDie after buying and the refund wipes until your next vendor purchase.
Be in it, or in spawnThe owner must be seated in the vehicle at match end - unless the vehicle is parked inside the spawn zone. That is the only exception.
Invisible timer: the 20-tick countdown is not shown in-game. The developer has called that bad design and is looking at it. Until then, count roughly 7-8 minutes from the moment you press buy.

2Before You Buy a Tank or Heli

3Should You Buy Right Now?

Match just started
Usually no
The 20-tick window will expire long before the end screen. A heavy buy at minute one is almost always full price gone.
Enemy armor/air is live
Yes, if you can stay in it
Kill bounties ($7k tank / $9k attack heli / $14k arty) can offset the unrefunded slice even if the window misses.
Leading team near 80-90+ points
Best time to buy
The match ends inside your window - this is when late buys actually refund. Be in the seat at the whistle.
Dropping the vehicle at FOB to fight on foot
Do not buy
You will not be in it at match end and it will not be in spawn. That is a guaranteed $0 refund.
Tight on cash? Cheaper armed transports - Ural Defender, armed Humvee, minigun Lakota - hurt far less when the 20-tick window misses.

Mistakes That Eat the Whole Purchase

How players play it: hold the heavy buy for the last 7-8 minutes, use the vehicle to print money inside the window (zone ticks, vehicle kills, passenger drops), then be sitting in it at the end. If the match is clearly going long, skip the L2A6 / Havoc / SPG and run logistics or a cheap armed truck.