I purchased FM5 on Day One and signed up for Forza Rewards. The website shows a running total of bonuses earned in FM4, FM5, FH, & FH2; does this mean the 900,000 FM4 credits which have accumulated over the past 21-odd months will be available in-game? Or do I receive rewards moving forward only?
No. Only from the current month / week, to the future.
http://forums.forza.net/turn10_postst262_Forza-Rewards-FAQ.aspx
You redeem the rewards via the website / hub, but you also need to retrieve the in-game message to be able to ‘download’ the gifted money.
Afaik … these messages can’t be retrieved for months in the past in all games on the 360.
It only works with the XB1 games. Seems to be a different message-system.
But just launch your FM4 and check your in-game mailbox.
I stand to be corrected, but think as long as you redeemed them, they will be to your credit in-game when you start FM4. I bought FM5 about a year after launch and received all my redeemed credits for all those months (while on FM4) when I started FM5. Same for FH2. Might be that the 360 works differently though.
At least for me it worked only on the XB1 to retrieve messages after the month they were sent.
Worked never on the 360.
Most of the time i was just to lazy to start FM3 , FM4 and FH1 every month just for the gifted credits. Especially the monthly rewards were very low on the 360 games and i already had everything completed.
But maybe it should work even on the 360 and it’s just another bug inside the whole reward system …
Found this in the link Noobertson sent 
So I should be able to get a higher tier before FM6, but unlikely I’ll be able to place 300 cars in the FM4 garage.
For an instant multi-million CR boost just ask here
or here
http://forums.forza.net/turn10_postst40012_Offering-Assistance-with-Car-Collector-Bonus.aspx
or here
http://forums.forza.net/turn10_postst32188p4_Money-for-the-poor.aspx
The answer is… none of the above. I ended up with 380,000 prior period credits.
Of the 960,000 credits rewarded indicated on the forzamotorsports.net web page, 320,000 of them showed up in each game a week or so after I started playing FM4 and FH.
When receiving the first rewards in September, I got not only the 20,000 expected but also another line entry in each game of 60,000 for… reasons not indicated in message.
It’ll take a greater mind than mine to figure this out, but happy with what I got. Also, raceboy77 came through with needed credits; thanks for the tip Noobertson!
De nada!
Btw: 380.000 is ok because:
The FM4 rewards in august had been WEEKLY 80.000 for your tier (7) = 320.000
The 60.000 you received are the rewards for july 2015 (tier 7) because you still grabbed them in the one month after july.
See the very end of post #2
http://forums.forza.net/turn10_postst262_Forza-Rewards-FAQ.aspx
The 60.000 for july are missing in his overview but you can see the difference for tier 6 and 7 for the other games.
The first weekly reward for september 2015 didn’t showed up in my account until today.
Anyway …
have fun in FM4!
The answer is… none of the above. I ended up with 380,000 prior period credits.
Of the 960,000 credits rewarded indicated on the forzamotorsports.net web page, 320,000 of them showed up a week or so after I started playing FM4 and FH.
When receiving the first rewards in September, I got not only the 20,000 expected but another line entry of 60,000 for… reasons not indicated in message.
It’ll take a greater mind than mine to figure this out, but happy with what I got.