Plasterboarding

Hi, I had recently attempted to plasterboard my kitchen ceiling. O have correctly fixed the plasterboards to the joists. Everything seems solid and secure. However my only problem is the ceiling was not properly square so I now have gaps around the edges, corners and between a few boards. How can I fill this so it is ready to be skimmed?

Any help appreciated
Thank you

I don't know enough to give any real advice but i've just done my bedroom ceiling with help from this forum, I put the long edge against the wall, noted the difference between the short edge and the wall then cut the board end to suit , then i just butted the next board up square against that then cut the last board to suit the opposite wall, repeated until the room was done , i've very few gaps and the ones that i do have are less than 5mm around the room perimeter and have no gaps where boards are butted against each other

I'm sure other plasterers will correct me - Wouldnt Plasterers jointing tape do the trick?

I fid try to cut the boards to fit against the walk but small gaps could not be avoided. I will br using joint tape over the staggered plasterboards however am pretty sure the gaps around the corners of the wall need filling with something. Hhhmmmm
Thanx anyway guys

If you're not going to plaster it yourself, then let the plasterer prep/fill the gaps etc.

but,,,

If "you" are going to attempt to plaster it yourself, them get some bonding coat plaster to fill up the gaps where required, ie, joints/around edges etc. Let the bonding more or less set,( i do it that way), then put tapes over the board joints, and also put tapes all around the wall/ceiling line. You're then ready for plastering.

An extra tip,,
"don't" put the tapes on first and expect the bonding plaster to fill up the gaps through the mesh, it wont work,, fill the gaps up first,, flush off neatly,, then tape. If any of the "bigger gaps" involve p/board edges that have been cut,, exposing the "dry edge/s" of the p/board, it's always worth them damping them down with a small brush, and also brushing on some PVA, "just before" you fill up the gap,, gives much better adhesion,,, so you fill the gap/s with the bonding, while the PVA is wet.