On one level, it isn't necessary to understand or believe in the Trinity for salvation.  ALL salvation related scripture makes no mention of the Trinity either directly or even by implication.

HOWEVER......................

Let's look at one of the many verses about salvation that are precise..."Because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved."

...you MUST "confess with your mouth that Jesus is..................??   L O R D ! !

...this means that you cannot confess that Jesus is a nice man, Jesus is a prophet or even Jesus is an archangel.......you must confess He is Lord.

Now this verse alone does not say He is God or that He is part of the Trinity, but irrespective of what you believe Jesus is or is not, the verse is clear that you in whatever capacity Jesus is Lord, you must know it in order to confess it!In other words, if Jesus is God, then salvation depends on you declaring He is that kind of Lord.  If Jesus is not God, then salvation depends on you declaring He is whatever kind of Lord He is.    Jesus must be part of the Trinity or not, and if you get that wrong then you don't know the real Jesus and you have no salvation!Jesus won't tolerate fence sitting when it comes to knowing who He is..."Jesus also said, “He who is not with me is against me, and he who does not gather with me scatters.” (Matthew 12:30) 

Why do people not understand such a simple concept and the way BAD Christian sects and cults are so against it?!

God the father - THE ONLY GOD!!!!!!!

The SON OF GOD - JESUS and NOT god.

The Holy Ghost - the SPIRIT of GOD - therefore it is of God not a different God!

Whilst Christianity is over 2,000 years old the three you mentioned are all modern fraudulent claims to be Christian!!!!!!!!!!!!!!

I don't agree

(even though I do believe in the doctrine of trinity)

but the reasoning behind the "if you don't believe in trinity then you are not saved" doctrine is as follows:

If you don't accept Jesus as God

even though he is God

then you reject Jesus

and you reject God.

Trinity is a false doctrine authorized by Empires Constatine in 325 A D . Jesus said in Mat. 19:17 to not call anyone but the Father good GT .

They aren't truly Christian, never mind saved.

The catholic church believes in the trinity of the Father, Son, & Holy Ghost as do the international churches of Christ (Boston crossroads movement) and even the Seventh day adventist's and others as well

Yet these churches teach a works system for salvation and not grace (Rom 4:4-5, 11:6, Eph 2:8-9) NOT of works e.g water baptism ceremonies, keeping the law, or doing good works etc,

Understanding the Godhead trinity (Matt 28:19, Rom 1:20 & 1John 5:7) is not a requirement for a person to be saved --- it is believing in Christ's death, burial, and resurrection for our sins by FAITH only (Acts 16:31, 1Cor 15:1-4,& Eph 1:13)

If having some understanding of the trinity or the virgin birth/conception or Christ's deity etc, helps a person to get saved in him --- then that's good but it is not essential to know those things to get saved -- I didn't know Jesus was God in the flesh (John 1:1,14) or the trinity was the Godhead (Acts 17:29 & Col 2:9) when I got saved.

I'm not saying that all trinity denying groups don't have people truly saved in Christ --- but it just wasn't through their system they got saved.

There is no "trinity doctrine" for it is only the interpretation of man.

Since Jesus, Peter, John and Paul didn't teach or believe in a trinity, salvation can not come from believing in it.

Otherwise, Jesus, Peter, John and Paul wouldn't be saved.

.

The trinity isn't exactly biblical so no